Preheat the oven to 200 C / Gas 6. Line a 12-hole muffin tin with paper cases.
In a bowl sift together the self-raising flour and baking powder. Mix through the chocolate chips.
In a separate bowl beat the peanut butter, sugar, eggs and milk until well combined. Fold the dry ingredients into the wet and mix until just combined. Divide the mixture between the 12 cases, filling only to half way to ensure a good rise.
Bake in the preheated oven for 15 to 20 minutes until a skewer inserted into the centre come out clean and the muffins are well risen and firm to the touch. Remove from the oven and allow to cool for 5 minutes before transferring to a wire rack to cool fully.
You can use either crunchy or smooth peanut butter, it’s down to personal preference or whatever you happen to have on hand. Obviously using crunchy will give the muffins more texture.