I love sandwiches that feel like a whole meal wrapped in bread. This Chicken Florentine Panini hits that mark: tender chicken, tangy-sweet caramelized onions, garlicky mayo, spinach for brightness, and melty provolone. It’s straightforward to make on a weeknight, but special enough for guests.

There’s a little bit of prep—caramelizing onions and flattening chicken—but none of it is technical. The result is a crisp, golden panini with layered flavors and a satisfying chew. Below I walk through every ingredient and step so you can make this reliably at home.

Ingredient Notes

1/4 cup mayonnaise — forms the garlicky spread that adds moisture and richness.

1 garlic clove, minced — gives a bright, fresh bite to the mayo; don’t skip it.

1 (10-ounce) tube refrigerated pizza crust — pressed and baked into four sandwich rectangles; it’s the bread for these panini.

1 1/2 tablespoons olive oil, divided — used for sautéing onions and for cooking the chicken and panini; split to control browning.

1 medium red onion, cut in half and thinly sliced — caramelizes into sweet, tangy layers when cooked with sugar and vinegar.

2 teaspoons granulated sugar — helps the onions caramelize and balances the vinegar.

1 tablespoon balsamic vinegar — adds acidity and depth to the onions; intensifies their sweetness.

1/4 teaspoon crushed red pepper flakes — a gentle heat that brightens the onion mix; adjust to taste.

2 boneless, skinless chicken breasts — the main protein; they’re pounded thin so they cook quickly and evenly.

salt and pepper — basic seasoning for the chicken; season both sides before cooking.

1/4 teaspoon dried thyme — subtle herb note that complements chicken and cheese.

1 (9-ounce) package frozen, chopped spinach, thawed and squeezed to get rid of liquid — adds color, nutrients, and a mild earthy flavor; make sure it’s well drained.

8 provolone cheese slices — melts smoothly and brings mild, slightly tangy creaminess to each sandwich.

Method: Chicken Florentine Panini

1. In a small bowl, combine 1/4 cup mayonnaise and 1 minced garlic clove. Stir until smooth and refrigerate until assembling sandwiches.

2. Preheat the oven to 375°F (190°C).

3. While the oven heats, heat 1/2 tablespoon of the olive oil in a large nonstick skillet over medium heat. Add the thinly sliced half of a medium red onion and sauté for 3 minutes, stirring so it softens evenly.

4. Add 2 teaspoons granulated sugar, 1 tablespoon balsamic vinegar, and 1/4 teaspoon crushed red pepper flakes to the skillet with the onions. Continue to sauté for about 5 more minutes, stirring occasionally, until the onions are soft and glossy. Transfer the onions to a bowl and set aside.

5. When the oven reaches 375°F, unroll the 10-ounce refrigerated pizza crust and press it into a 15×10-inch jellyroll pan so it fits evenly. Bake the crust for 10 minutes until lightly set and just starting to color. Remove from the oven and let cool. Once cool enough to handle, cut the baked crust into 4 equal rectangles.

6. Wipe the skillet clean and use it to cook the chicken next. Flatten the 2 boneless, skinless chicken breasts with a meat mallet or rolling pin until each is about 1/4 inch thick. Season both sides with salt, pepper, and 1/4 teaspoon dried thyme.

7. Heat the remaining 1 tablespoon olive oil in the cleaned skillet over medium-high heat. Add the flattened chicken breasts and cook 4 to 5 minutes per side, until cooked through and no longer pink in the center. Transfer the cooked chicken to a cutting board and let rest for 5 minutes, then slice into pieces suitable for sandwiching.

8. To assemble the panini, spread the refrigerated garlic-mayonnaise mixture on one side of 2 of the baked dough rectangles. On the other 2 rectangles, arrange the sliced chicken, the squeezed and drained frozen chopped spinach, and the cooked onions. Top each layered rectangle with 2 provolone cheese slices (use 4 slices per sandwich). Place the mayo-spread rectangles on top, mayonnaise side down, to form two sandwiches.

9. Lightly grease a cast-iron skillet with a little olive oil and heat it over medium-high heat. Add the assembled sandwiches to the skillet. Cook until the bottom is golden brown, pressing down gently with a spatula to compact the sandwich. Flip and cook the second side until golden brown and the cheese is melted, about 3–4 minutes per side depending on heat.

10. Remove the sandwiches from the skillet, cut each in half, and serve immediately.

Why This Recipe Is Reliable

– The chicken is pounded to 1/4 inch so both breasts cook in the same short window; no guessing internal temperatures.
– Baking the pizza crust first prevents sogginess from the spinach and onions and gives a sturdy bread-like base.
– Separating the mayonnaise spread and heating steps keeps the mayo cool and flavorful instead of melting away under heat.
– A simple seasoning set (salt, pepper, thyme) allows the caramelized onions and balsamic to shine without overpowering the chicken.
– Cooking order minimizes cross-contamination: onions → bake crust → wipe skillet → cook chicken → assemble → panini. That sequence also makes prep efficient.

Swap Guide

Bread: Use ciabatta or focaccia slices instead of baked pizza crust for a heartier texture.

Cheese: Swap provolone for mozzarella for milder melt or fontina for a richer flavor.

Greens: Fresh baby spinach (lightly wilted) can replace frozen spinach; reduce moisture so sandwiches don’t get soggy.

Heat: Increase crushed red pepper flakes or add a thin layer of spicy mustard to the mayo for more kick.

Vinegar in onions: Sherry vinegar works well if you don’t have balsamic.

Tools of the Trade

Large nonstick skillet — for sautéing the onions and cooking the chicken; the nonstick surface helps prevent tearing.

Meat mallet or rolling pin — to flatten chicken to an even 1/4-inch thickness for quick, even cooking.

15×10-inch jellyroll pan — to press and bake the pizza crust into sandwich-sized rectangles.

Cast-iron skillet — provides even heat and a great crust on the panini; a heavy pan is ideal for pressing.

Small bowl and spatula — for mixing the mayo and garlic and for spreading.

Missteps & Fixes

Onions not caramelizing: If onions steam instead of caramelize, raise the heat slightly and stir more frequently to encourage browning. Make sure the pan isn’t overcrowded.

Wet spinach: Excess moisture will make the panini soggy. Squeeze thawed spinach in a towel or fine sieve until dry before assembling.

Chicken overcooked/dry: Don’t skip pounding the breasts thin—thicker pieces overcook on the outside before the center is done. Cook 4–5 minutes per side for pounded breasts.

Crust soggy after assembly: Baking the pizza crust first is essential. If yours still ends up soft, toast the assembled sandwich a little longer over medium heat or press more firmly while cooking.

Dietary Swaps & Alternatives

Lower-fat: Use light mayonnaise and reduced-fat provolone, or swap mayo for Greek yogurt mixed with garlic (same quantity).

Gluten-free: Use a store-bought gluten-free pizza dough or gluten-free bread slices in place of the pizza crust.

Vegetarian: Omit chicken and add grilled portobello mushroom slices or marinated tofu cut thin to mimic the texture and heft.

Dairy-free: Replace provolone with a plant-based melting slice and use dairy-free mayo.

Testing Timeline

Onion cook time: Plan 8 minutes total: 3 minutes to soften, then 5 minutes with sugar and vinegar to develop sweetness and color.

Pizza crust bake: 10 minutes at 375°F to set and slightly color; allow to cool before cutting so it doesn’t compress.

Chicken: 4–5 minutes per side for 1/4-inch pounded breasts; rest 5 minutes before slicing.

Assembled sandwich cook: About 3–4 minutes per side over medium-high heat until both sides are golden and cheese is melted. Watch closely—times vary by skillet and stove.

Store, Freeze & Reheat

Store: Finished panini are best eaten fresh. Leftovers keep in an airtight container in the refrigerator for up to 3 days.

Freeze: You can freeze fully assembled but un-toasted sandwiches wrapped tightly in plastic and foil for up to 1 month. Thaw overnight in the fridge before toasting.

Reheat: Reheat in a skillet over medium heat or in a toaster oven to restore crispness. If microwaving, cover and use short bursts to avoid sogginess, then crisp in a hot skillet for 1 minute per side.

Reader Q&A

Q: Can I use fresh spinach instead of frozen? — A: Yes. Use a handful of fresh baby spinach leaves and briefly wilt them in the pan with a splash of oil before assembling. Pat dry so sandwiches remain crisp.

Q: Can I make these on a sandwich press? — A: Absolutely. A press works well and shortens cook time; watch for even browning and melted cheese.

Q: Can I prep components ahead? — A: Yes. Make the onions and garlic mayo up to 2 days ahead; bake the crust and store airtight. Cook chicken same day for best texture.

Let’s Eat

Slice your panini while hot to reveal gooey provolone, glossy caramelized onions, and tender chicken layered with spinach. Serve with a simple green salad or a cup of tomato soup for a classic pairing. These panini travel well for picnics if wrapped warm, and they’re easy to scale if you’re feeding a crowd. Enjoy.

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