Combine Brownie mix, oil, eggs and vanilla in large bowl with wooden spoon until blended.

Refrigerate 1 hour or overnight.

Preheat oven to 350°F.Line baking sheets with parchment paper. Set aside.

Remove cookie dough from fridge. Using a large ice cream scoop, place dough on to parchment lined cookie sheet, keep dough about 2 inches apart.

Bake cookies for 10-15 minutes until edges look done. Cool cookies 1-2 minute on pan then remove to cooling rack. Cool completely on wire rack.

When cookies are cool pipe chocolate fudge frosting on bottom of brownie. Top with second brownie, bottom on top of frosting. Press lightly together (you want the frosting to peek a bit outside the edge of the cookie). Roll edge of whoopie pie in sprinkles. Enjoy.