Prepare the brownies according to the directions on the box. Be sure to use a 9x13 baking pan.
Once the brownies are baked, allow the brownies to completely cool before cutting them into the triangles.
Carefully transfer the brownies from the pan to a large cutting board.
Evenly cut the brownies into 3 equal horizontal sections.
Cut 4 diagonal sections to make a diamond pattern.
Then cut the diamonds in half. This should give you 18 full-shaped triangles.
Line a baking sheet with parchment paper.
Transfer the triangles to the prepared baking sheet.
Using an offset spatula, neatly ice the halved diamonds.
Place an M&M at the bottom of one of the triangle ends for the nose.
Place 2 of the candy eyeballs in the center of the triangle.
Then place 1 pretzel “antler” on the remaining 2 triangle points.
Another option is to use a heart-shaped cookie cutter. Beginning on the top edge of the brownies, and working toward the opposite end, cut out the hearts.
Carefully frost the heart-shaped brownies with the chocolate frosting.
Just above the point of the heart, place the brown or red M&M for the nose.
Place the eyes in the center of the heart.
Just before serving, place the antlers.