Preheat oven to 180C/350F.
In a pan over low heat, start browning your butter. DON'T WALK AWAY. Keep stiring until the milk solids and golden. Remove and set aside to cool for 15 minutes.
Add in the sugars with the brown butter and mix until combined. Then followed with the yolks and whisk again. Add in the flour, baking soda and choc chips, and mix until cookie dough forms.
Cut and open up your croissants and place them on a lined baking sheet. Fill the insides with cookie dough, close the croissants and top with more cookie dough. Bake for 13 minutes or until the cookie is golden.