Prepare brownie batter by mixing the dry mix, oil, water, and eggs according to package directions. Line 24 mini muffin cups with paper mini cupcake liners.
Scoop batter, 2 teaspoons full at a time, into each mini muffin cup. Sprinkle chocolate chips evenly over batter in muffin cups. Bake at 350 degrees for 6 - 9 minutes or until brownies are almost cooked through. Allow brownies to cool completely.
Frost brownie bites with chocolate frosting using the filled pastry bag. Sprinkle with chocolate jimmies. Serve immediately.