In a mixing bowl whisk together 3/4 cup chia seeds, 2 1/4 cups nut milk, 1/2 cup cacao (or unsweetened cocoa) powder, 1/3 cup maple syrup, 1 teaspoon vanilla extract, and 1/2 teaspoon flaky sea salt until fully combined.
Cover the bowl and refrigerate the mixture for at least 2 hours or up to overnight to allow the chia to swell and thicken.
Transfer the chilled chia mixture to a blender and blend on high until smooth and creamy, scraping down the sides once or twice; taste and add more maple syrup if a sweeter mousse is desired.
Spoon the blended mousse into six serving bowls, cover, and chill for 2 hours or until set.
To make the whipped coconut cream, invert the can of 14-ounce unsweetened coconut cream and pour off any liquid. Scoop the solid coconut cream into a bowl, add 2 tablespoons maple syrup (or honey) and 1/2 teaspoon vanilla, and whip with an electric mixer until smooth and slightly fluffy.
Serve each mousse topped with a dollop of whipped coconut cream and, if using, sprinkle dried roses and cacao nibs on top.
(Optional) For coconut cream hearts: line an 8x8-inch pan with parchment, spread the whipped coconut cream evenly, freeze 20–30 minutes, then use a heart cookie cutter to cut shapes.