01 -
In a small saucepan, combine 1 cup water, 2 Tbsp sugar, and 4 Tbsp rum. Bring to a simmer for 1 minute, stirring until the sugar dissolves. Remove from heat and let cool to room temperature.
02 -
If using whole almonds, combine 1/2 cup sugar, 2/3 cup almonds, and 1/8 tsp salt in a food processor and pulse until finely ground. Add the butter and blend until smooth. Add the eggs one by one and process on high speed until creamy and fluffy. If using almond meal or almond flour, combine 1/2 cup sugar, 1 cup almond meal, and 1/8 tsp salt in a mixer fitted with a whisk attachment. Mix until incorporated, then blend in the butter. Add the eggs one by one and mix on medium-high speed until creamy and fluffy.
03 -
Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper. Slice each croissant horizontally like a sandwich. Dip each croissant into the syrup, ensuring both sides and ends are coated but not soaking wet. Arrange the croissants on the prepared baking sheet with the cut side up. Spread about 2 Tbsp of almond filling on the bottom half of each croissant. Place the top halves over and spread about 1 Tbsp of almond filling over the top. Sprinkle with sliced almonds.
04 -
Bake in the center rack for 15 to 18 minutes, or until the almond filling is golden. Transfer to a wire rack and cool to room temperature or slightly warm. Dust with powdered sugar before serving.