Preheat your oven to 350°F.
Line a 9 x 9 inch pan with parchment paper, leaving some overhang so you can lift them out.
Whisk flour, cocoa powder, and salt in a bowl until everything looks evenly mixed.
Stir vegetable oil, brown sugar, granulated sugar, and melted butter together in a separate bowl until smooth.
Add eggs, corn syrup, and vanilla, then mix until the batter turns glossy and thick.
Fold the dry ingredients into the wet just until you don’t see any flour streaks.
Spread the batter in the prepared pan using a spatula.
Bake about 25 minutes. The center should show moist crumbs if you poke it with a toothpick.
Let the brownies cool in the pan before you add the topping.
Heat heavy cream in a small saucepan until it starts to steam.
Pour the cream over the chocolate chips, wait a minute, then stir until smooth and shiny.
Spread ganache over the cooled brownies in an even layer.
Sprinkle rainbow candy-coated chocolate chips on top, then refrigerate until set.