Combine 60ml water and 2 tbsp granulated sugar in a small saucepan over medium heat. Simmer for 2 minutes until dissolved, then remove from heat and cool for 5 minutes.

Beat 50g softened butter and 60g sifted powdered sugar until pale and smooth, about 2 minutes. Add 1 egg, 1/2 tsp almond extract, and 1/2 tsp vanilla extract and mix for 30 seconds. Fold in 60g almond flour until a thick paste forms.

Preheat oven to 350°F (175°C) and line a baking sheet with parchment. Slice each croissant horizontally, brush cut surfaces with syrup, spread frangipane on the bottom half, and press the top back down.

Spread remaining frangipane over the top of each croissant, press on 30g sliced almonds, and bake for 14 to 16 minutes until the topping is golden and just set.

Rest on a wire rack for 3 minutes, dust with 2 tbsp powdered sugar through a fine-mesh sieve, and serve warm.