Preheat the oven to 350°F (175°C). Line a mini muffin tin with liners.
In a bowl, whisk together cake flour, baking powder, and salt; set aside.
Cream 1/2 cup (1 stick) softened butter with 1/2 cup granulated sugar on medium speed for 3–5 minutes until light and fluffy.
With the mixer running, add 1/2 cup maple syrup, 1/2 tsp vanilla, then the eggs one at a time, beating well after each addition; add 1/3 cup milk and mix to combine.
Add the flour mixture to the wet ingredients in roughly 1/2-cup increments, mixing until just combined; avoid overmixing.
Toss 1/2 cup mini chocolate chips with about 1/2 tablespoon of the reserved flour mixture to coat, then gently fold the chips into the batter.
Spoon batter into the prepared mini liners, filling each about 3/4 full.
Bake at 350°F for 7–9 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the tin briefly, then transfer to a rack to cool completely.
To make the maple buttercream: beat 1/2 cup (1 stick) softened butter with 3 cups powdered sugar, 1/4 cup maple syrup, and 2 tsp Tahitian vanilla until smooth and creamy, about 3–5 minutes.
If the frosting is too thick, add up to 1 tbsp milk to reach spreading consistency, then beat to combine.
Frost cooled mini cupcakes as desired.