Makes 3 dozen cookies.
Over a pot filled with 2 inches of simmering water, place a metal or glass bowl and add butter. Stir until melted halfway and add white chocolate chips. Stir until just melted and remove from heat (don’t worry if it separates). Set aside.
Whip eggs with sugar and vanilla with electric beaters or in a mixer fitted with the whisk attachment, until pale and thick, about 5 minutes. In a separate bowl, combine flour, baking powder and salt.
Whisk melted chocolate into egg mixture until incorporated. Whisk in flour mixture and stir in semisweet chocolate chips. Cover batter with plastic and chill for at least 4 hours before baking.
Preheat oven to 325 °F. Spoon cookie dough by tablespoonfuls (or teaspoonfuls for dainty cookies) and roll gently to shape into a ball and place on a parchment-lined or greased cookie sheet, leaving 2 inches between cookies. Bake for 18-20 minutes. To test doneness, lift a cookie off the tray – if it comes off cleanly, then cookies are done.
Reverse Double Chocolate Chip Cookies
Mmmm – gooey dark chocolate cookies with white chocolate chips! Prepare the same recipe as above, except replace 8 ounces of white chocolate with 10 ounces of bittersweet chocolate and increase sugar to 1 1/2 cups. Prepare remaining recipe as above and enjoy!