In a bowl, take the Nutella and add melted butter., melt it in a microwave or on a double boiler on the stove. Give it a good mix until well combined and looks smooth 

In another bowl, combine the milk and sugar and melt it on the stove until all of the sugar has dissolved. Add to the Nutella and butter mixture

Now add maida and cocoa powder, whisk until the batter is well mixed. Pour in a prepared tin lined with parchment paper. Bake in the oven at 180° C for 23 - 24 mins or until a toothpick comes out clean with just a few moist crumbs. Let the brownie cool at room temperature for about 20 minutes. Take it out of the tin and let it cool on a cooling rack completely until cooled to room temperature.

For the ganache, heat cream in a saucepan on medium-high until just boiling. Pour cream over the chocolate chips and stir to melt. Add butter Ganache is ready once the chocolate is completely melted. Decorate the brownie with ganache or just spread it over