Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In another bowl, sift together the flour, cocoa powder, baking powder, and salt.

Gradually add the dry ingredients to the wet mixture, stirring until just combined.

Fold in the chopped Maltesers and chocolate chips.

Pour the batter into the prepared baking pan and spread it evenly.

Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.

Allow to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.

For the topping, heat the heavy cream in a small saucepan over medium heat until it begins to simmer.

Remove from heat and add the chocolate chips, stirring until melted and smooth.

Pour the chocolate ganache over the cooled tray bake and spread evenly.

Top with whole Maltesers, pressing them gently into the chocolate.

Let the tray bake set for at least 1 hour before cutting into squares.