In a medium saucepan, melt ½ cup of unsalted butter and 1 cup of semi-sweet chocolate chips over low heat. Stir continuously to ensure a smooth mixture without burning, about 5 minutes. Remove from heat and let cool for 10 minutes.

Whisk in 1 ½ cups of granulated sugar into the cooled mixture until fully dissolved. Add 3 large eggs one at a time, mixing well after each. Then add 1 teaspoon of vanilla extract.

In a separate bowl, whisk together 1 cup of all-purpose flour, ⅓ cup of unsweetened cocoa powder, and ½ teaspoon of salt until well combined.

Gradually fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix.

Preheat oven to 350°F (175°C). Grease a 9x13-inch baking pan. Pour the batter into the prepared pan and spread evenly. Bake for 20-25 minutes, checking for doneness with a toothpick.

Let the brownies cool for at least 15-20 minutes before frosting. Spread a layer of chocolate frosting evenly on top and use chocolate chips and candies for decoration.