Melt 1 cup of unsalted butter in a medium saucepan over low heat. Stir occasionally and cool for 5 minutes.

In a large mixing bowl, mix the cooled melted butter with 2 cups of granulated sugar until smooth and glossy.

Add 4 large eggs one at a time, mixing well after each, and then stir in 1 teaspoon of vanilla extract.

In another bowl, whisk together 1 cup of all-purpose flour, 1 cup of cocoa powder, ½ teaspoon of salt, and ½ teaspoon of baking powder. Gradually mix into wet ingredients until just combined.

Pour batter into a greased 9x13 inch baking pan and preheat the oven to 350°F (175°C).

Bake for 25-30 minutes, checking for doneness with a toothpick. Allow to cool completely.

Dip tops of chocolate ice cream cones in melted chocolate and roll in sprinkles. Let set.

Combine 2 cups of powdered sugar, ¼ cup of milk, and 1 teaspoon of vanilla extract until smooth. Add green food coloring to desired shade.

Frost the cooled brownies evenly with the green frosting.

Carefully place an upside-down chocolate cone on each frosted brownie and sprinkle with Halloween decorations.