1. Preheat the oven.
Set your oven to 350°F (175°C). Lightly grease a mini muffin pan or line it with mini paper liners to make removing the brownie bites easier.

2. Mix the brownie batter.
In a large bowl, combine the brownie mix, eggs, oil, and water. Stir just until combined — avoid over-mixing to keep the brownies dense and chewy.

3. Fill and bake.
Spoon the batter evenly into each mini muffin cup, filling about two-thirds full. Bake for 12–15 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

4. Cool completely.
Let the brownie bites cool in the pan for 5 minutes, then transfer them to a wire rack. Cool completely before frosting.

5. Make the frosting.
In a separate bowl, beat softened butter with an electric mixer until light and creamy. Gradually add powdered sugar, one cup at a time, mixing on low speed. Add vanilla extract and milk (or cream), then beat for 3–5 minutes until fluffy. Tint with green gel food coloring until you reach your desired shade.

6. Decorate.
Pipe or spread the frosting onto each brownie bite. Gently press a candy eyeball (or several, for multi-eyed monsters) into the center. Use a toothpick dipped in red gel coloring to draw tiny veins for a spooky touch.