Melt the butter in a small saucepan over medium-low heat, stirring and scraping the pan every 10-15 seconds. The butter will melt, foam, then turn golden brown with nutty aroma and small brown bits (about 5-7 minutes). Remove from heat and add cocoa powder and milk or dark chocolate bar in hot butter.Mix thoroughly till there’re no lumps in it and set it aside to cool.

Preheat the oven at 166C (fan oven) if you’re using dark colour aluminum pan or at 176C (fan oven) if using lighter colour aluminum pan.

Line a muffin baking tray with butter and muffin liners, for easy removal.

In a bowl add eggs, white sugar, light brown sugar, whisk together until most or all of the sugar granules have dissolved.

Once the sugar has dissolved, add the brown butter, cocoa powder, melted dark or milk chocolate mixture and vanilla extract. Mix everything together.

Add the all-purpose flour and salt and mix just until combined, avoid overmixing.

Pour the batter into the prepared cup cake liners and bake for about 30-40 minutes.

Begin checking at the 30 minutes mark by inserting a tooth pick into the center. The brownie cups are done when the edges are set and the tooth pick comes out with a little batter still clinging to it. Depending on your oven, total bake time may be up to 40 minutes. Let them cool down completely

Melt milk chocolate using the double boiler method, then mix in chopped roasted hazelnuts.

Carefully remove the cupcake liners and coat each brownie cup evenly with the hazelnut chocolate. Let them set for 20–30 minutes.

Using a piping bag, fill the cups with duo hazelnut spread.

Top each one with a Fe