Mix the dry ingredients

• Put the cocoa powder, protein powder, flour, sweetener, baking powder and salt in a mug.
• Stir with a spoon until evenly combined and no lumps remain.

Add the milk

• Pour in the milk and stir until you get a thick, smooth batter.
• Scrape down the sides of the mug so the batter is level.

Insert the chocolate centre

• Push the piece of dark chocolate into the middle of the batter so it is fully covered.

Microwave

• Microwave on high until the cake has risen and the top is just set, keeping the centre molten.
• Do not overcook or the centre will dry out.

Serve

• Let the mug cake rest for a moment, then eat straight away while the chocolate centre is still melting.