Begin by making the homemade buttercream. Add ¼ cup softened butter and 1 cup icing sugar into a large bowl. Add 1 tbsp milk and use an electric hand blender to mix all the ingredients together. Mix on medium-high speed for 3 minutes until smooth.

Add ¼ tsp of green gel food coloring to the buttercream and mix until completely tinted. Scoop the green buttercream into a piping bag with Wilton tip #5 attached.

Place the brownies so that the smaller end becomes the bottom. Add green buttercream to the top, with no particular pattern and top off with small dollops of buttercream.

Snap pretzel sticks in half and add one half into the frosted brownie. This will act like the cauldron’s spoon.