Chop the chocolate into chunks. Melt half (refer notes), then save the other half for later. Cool the melted chocolate till it's cool enough to touch.
Mix the butter and the sugar, then beat in the eggs and vanilla for 1-2 minutes until the mixture has become fluffy and light in color.
Whisk in the reserved melted chocolate (make sure the chocolate is not too hot or else the eggs will cook), then sift in the flour, cocoa powder, and salt.
Fold the dry ingredients into the wet ingredients, being careful not to overmix as this will cause the brownies to be more cake-like in texture.
Fold in the chocolate chunks, then transfer the batter into a parchment paper-lined square baking dish. (refer notes). If using nutella, add spoonfuls on top of the batter and gently drag it through the batter with a butter knife.
Bake for 20-25 minutes, depending on how fudgy you like your brownies, then cool completely.
Slice, then serve with a nice scoop of ice cream or cold glass of milk or some whipping cream!
Notes
I used Morde brand dark compound chocolate.I melted the chocolate using the double boiler method. Place chocolate in a large heat-proof bowl set over a pan of simmering water; stir until melted and combined. Remove from heat, and let cool for around 15 mins.Used an 8-inch square tin for baking.I baked it for around 25 - 28 mins.