01 -
Allow croissants to come to room temperature. Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
02 -
Cream butter with both sugars until light and fluffy. Add egg and vanilla, then mix until smooth. In a separate bowl, whisk flour, baking soda, cornstarch, and salt. Combine with wet mixture. Fold in chopped chocolate.
03 -
Slice croissants open. Spread 2 to 3 tablespoons of cookie dough inside each, keeping it away from the edges. Close gently to avoid squeezing layers.
04 -
Place filled croissants on baking sheet with space between. Sprinkle lightly with flaky sea salt if desired. Bake for 10 to 12 minutes until golden and cookie dough is just set.
05 -
Cool crookies on the baking sheet for 5 minutes before serving. Serve warm for best texture. Optional: pair with ice cream or fresh berries.