Heat oven to 180C/160C fan/gas 4. Lightly oil the inside of the terracotta pots with a little vegetable oil and place on a baking tray. Place a paper mini muffin case in the bottom of each pot.
Put the flour, baking powder and cocoa in a bowl and stir in the sugar.
Crack the egg into a jug and whisk with the milk and remaining oil. Pour this over the flour and cocoa mixture, and stir in with 50g of the chocolate chips. Be careful not to overmix – you want a loose but still quite lumpy mixture. Spoon into the pots up to three-quarters full. Place in the middle of the oven and bake for 12-15 minutes until risen and firm. Transfer to a wire rack (still in the pots) and leave to cool.
Put the rest of the chocolate chips in a small bowl and melt over a small pan of gently simmering water (don’t let the water touch the bowl), or put in a microwave-proof bowl and heat on High for 1 minute until melted.