Preheat your oven to 350°F. Grease a 8x8 inch baking pan or line it with parchment paper for easy removal.
In a large microwave-safe bowl melt the butter.
With a wooden spoon combine the melted butter and sugar. Mix well until smooth and sugar is fully incorporated. Add in the beaten eggs and vanilla extract, and beat until well combined.
Sift in the cocoa powder, flour, and salt into the wet mixture. Stir until just combined, but don’t overmix.
Gently fold in the caramel-toffee bits into the batter until evenly distributed. Pour the brownie batter into the prepared baking pan and spread it evenly with an offset spatula.
Place the pan in the preheated oven and bake for about 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, but not wet batter. Allow brownies to cool in pan for 5 minutes then transfer to a wire rack to cool completely.
Prepare the glaze in a microwave-safe bowl or using a double boiler. Melt the chocolate chips and butter together until smooth. Stir in the corn syrup until well combined.
Once the brownies are baked and cooled, spread the chocolate glaze over the top of the brownies, spreading it out evenly with an offset spatula.
While the glaze is still wet, sprinkle the rainbow sprinkles generously over the top!
Allow the glaze to set before slicing and serving the brownies. Serve and enjoy!