Ice Cream Sandwiches:
Preheat oven to 350 degrees F (177 degrees C) and place rack in center of oven. Line two baking sheets with parchment paper.
Chocolate Cookies:
1/2 cup (113 grams) unsalted butter, room temperature
1/2 cup (110 grams) light brown sugar
1/4 cup (50 grams) white granulated sugar
1 large egg
1 teaspoon pure vanilla extract
1 cup (140 grams) all purpose flour
1/4 cup (30 grams) Dutch-processed cocoa powder
1/2 teaspoon baking powder
1/4 teaspoon baking soda
1/8 teaspoon salt
OPTIONAL
1 1/2 cups (250 grams) white chocolate chips or coarsely chopped white chocolate