I made the dough the night before and left it in the fridge, then added the chopped chocolate the next day into each individual cookie while forming it (because I had to go buy some...). I kept them on a baking sheet in the fridge until ready to bake just to make sure everything was chilled fully. My tips would be to to brown the butter by following the instructions exactly (5 minutes stirring constantly, no stopping, and take it off the heat for a bit if it gets too foamy) and cream the butter and sugar for a veeeeeery long time, longer than you might think. I left the melted butter cooling in the fridge for an extra 10 minutes and that also helped, I think. I had leftover dough for another ~10 cookies after making 21 for a Super Bowl party, and they're wonderful even without the chocolate.
