• Line a 9x13 inch sheet pan with plastic wrap. Drop soft 1½ quart ice cream by the scoop over pan, then spread to edges. Cover with plastic wrap or parchment paper, and freeze for up to 1 hour.
• Preheat oven to 350˚F and line two 9x13 inch pans with parchment paper.
• Using a stand mixer and mixing bowl, add ½ cup butter with ¼ cup sugar and ½ cup brown sugar Beat until fluffy.
• Add 1 large egg, 1 teaspoon vanilla, and ½ teaspoon kosher salt. Blend until light in color.
• Slowly add 1¼ cup flour, ½ cup cocoa, ½ teaspoon baking soda, and ½ teaspoon espresso powder (if using) to the sugar mixture. Blend for 1 minute until smooth. Warm ½ cup milk for about 40 seconds in the microwave, add to the mixture, and blend for 1 minute more. The batter will be thick.
• On two parchment lined pans, drop dough by spoonful. Spread dough to edges as evenly as possible.
• Bake for 8 minutes. Remove from oven and pierce randomly with a fork or leave plain. Cool completely on a wire rack. Transfer to freezer for 2 hours or overnight.

Assembly

• Once ice cream and cookie layers are frozen, remove any plastic or parchment paper. Layer cookie, ice cream, and second cookie.
• Press down gently. Set back into freezer until firm enough to cut without squishing out the ice cream
• Cut into 10 rectangles and serve immediately. Or wrap each in plastic and store in freezer.