Preheat the oven to 375°F (190°C) then line a rimmed baking sheet with parchment paper.

Make the frangipane. In the bowl of a stand mixer, place ½ cup (48g) almond flour, 3 Tbsp (40g) sugar, 2 Tbsp (28g) unsalted butter, and a pinch of kosher salt. Beat on medium speed until well combined, about 2 minutes. Add 1 egg and 1 tsp almond extract, then beat on medium to medium-high speed until light and fluffy, about 2 minutes more.

Make simple syrup. In a medium saucepan, combine 1 cup (250ml) water and ½ cup (100g) sugar. Set over medium-high heat, then bring to a boil, stirring occasionally. When the sugar has dissolved, remove from the heat, then stir in 3 Tbsp amaretto. Cool slightly.

Prepare the croissants. Using a serrated knife, slice each croissant in half horizontally.

Dip in simple syrup. Take the bottom half of each croissant and dip it generously into the simple syrup, submerging it fully. Allow excess to drip off, then transfer to the baking sheet. Repeat with all 4 halves. Do not dip the top croissant.

Assemble the croissants. Fill the croissants by spreading 2 tablespoons of filling on each bottom half. Place the top half over the filling and press firmly to flatten. Brush with a bit of the remaining simple syrup, then evenly spread the remaining frangipane on top. Finish with a generous sprinkle of sliced almonds.

Bake the croissants. Transfer to the oven and bake for 15-18 minutes. Allow to cool for 10 minutes, then dust with powdered sugar. Enjoy warm or at room temperature!