Preheat oven to 350F/171C. Grease and line an 8-inch square pan.

In a saucepan over low heat, melt the butter. Add in the sugar and continue stirring, for about 1-2 minutes. Do not let the mixture boil.

Stir in Nutella. Beat in cocoa powder, eggs, salt, baking powder, instant coffee powder and vanilla extract.

Sift the flour over the cocoa mixture. Mix until well combined.

Pour mixture over prepare pan. Place tablespoonfuls of nutella over the top of the brownie batter, swirl using a dinner knife or a skewer.

Bake for 25-30 minutes or until set.