Firstly cream the butter and sugar in a bowl, then beat in the egg. Having sifted the dry goods add to mixture and mix gently. Then add the milk and mix till just combined.
Break the chilli chocolate into chunks.
First spray a muffin tin with oil then line with baking paper. Cut the paper into squares the overhang the muffin cups and spoon in the muffin mixture. Then push the chocolate into the centre of the muffins and place in a pre-heated oven at 200 for approx. 15 mins.
I use the baking paper because the chocolate melts and creates a very moist centre which can sometimes stick to the base of the tin.