Instructions:
Position rack in middle of oven. Preheat oven to 350ºF.  Lightly butter an 11 x 17 inch jelly-roll pan and line with parchment paper.

To make chocolate cookie: In a medium bowl whisk together flour, cocoa powder, salt, and baking soda until thoroughly blended. In a medium bowl whisk together melted butter, eggs, sugar and corn syrup until well combined, about 1 minute. Stir in dry ingredients and mix until blended. Spread batter evenly into prepared pan. Bake just until cookie springs back when lightly touched, about 9 minutes. Cool in pan 5 minutes. With a small knife, loosen cookie from sides of pan and invert on a parchment lined work surface. Carefully remove parchment from bottom of cookie and let cool completely, about 30 minutes. Line a baking sheet with plastic wrap. Cut cookie in half to make two 8 ½  x 11 inch pieces. Lay one half, top side down on the baking sheet.

To assemble ice cream sandwiches: Remove ice cream lid and let container stand at room temperature to soften, 10-15 minutes, stirring occasionally to encourage even softening. Spoon softened ice cream on top of cookie on baking sheet. Working quickly, using a rubber or metal spatula, spread ice cream evenly, making a layer of ice cream ½ - to ¾-inch thick. Top with remaining cookie half, top side up. Press gently to spread ice cream to the edges. Cover and freeze until firm, about 4 hours or overnight.
 
To serve: Remove baking sheet from freezer. Lift bottom piece of plastic wrap to remove sandwich from pan and place on work surface. Cut into 15 equal portions. Serve immediately or wrap individually and store in freezer for up to one week.  

Makes 15 sandwiches