01 -
Heat butter in a saucepan over low heat until sizzling. Once the moisture evaporates and the sizzling stops, allow the milk solids to turn brown (about 1-2 minutes), then turn off the heat. Avoid burning the butter by closely monitoring.
02 -
Transfer browned butter to a heatproof mixing bowl and let it cool. Add sugar and brown sugar, whisking until combined. Mix in the egg and vanilla extract.
03 -
Sift flour and baking soda into the bowl. Stir, then add ⅓ cup dark chocolate chips, mixing until just combined.
04 -
Slice croissants into halves. Flatten 2 tablespoons of cookie dough and place inside each croissant. Add extra chocolate chips, then close the croissant. Place 2 tablespoons of cookie dough on top of each croissant and add more chocolate chips for an appealing presentation.
05 -
Preheat the oven to 175°C (350°F). Arrange the crookies on a baking sheet and bake for 12 minutes, or until golden brown. Cool for 2-5 minutes before transferring to wire racks. Sprinkle with sea salt if desired.