Preheat the Oven:

Preheat your oven to 350°F (175°C) and grease or line a 9x13-inch baking pan with parchment paper for easy removal.

Mix the Wet Ingredients:

In a large bowl, whisk together the melted butter, granulated sugar, eggs, and vanilla extract until smooth and combined.

Add the Dry Ingredients:

In a separate bowl, sift together the cocoa powder, flour, salt, and baking powder. Gradually add the dry ingredients to the wet ingredients and stir until combined.

Add the Milk:

Pour in the milk and mix until the batter is smooth and glossy.

Bake the Brownies:

Pour the brownie batter into the prepared pan and spread it evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter).

Prepare the Topping:

While the brownies are baking, melt the semisweet chocolate chips and butter together. You can do this in a microwave-safe bowl in the microwave in 20-second intervals, stirring between each, or using a double boiler. Stir until the chocolate is smooth and fully melted.

Top the Brownies:

Once the brownies are done baking, remove them from the oven and allow them to cool in the pan for about 10-15 minutes. Then, pour the melted chocolate topping over the brownies and spread it evenly with a spatula.

Add the Candies:

While the chocolate is still soft, sprinkle the candy-coated chocolates (like M&M's) over the top, pressing them gently into the chocolate layer.

Cool and Serve:

Allow the brownies to cool completely in the pan before slicing them into squares. The chocolate topping will set as they cool.