Lightly grease or line with cases your muffin pan.
Pre heat your oven to 220C / 425F / Gas mark 7.
In a medium sized mixing bowl mix the flour, baking powder, baking soda, salt and chocolate chips together until well mixed and place to one side.
In another medium sized bowl or large jug put the egg, both sugars, vegetable oil and buttermilk in together and whisk until everything is well combined.
Once well combined add in the vanilla, applesauce and peanut butter and whisk again until you have a smooth liquid.
Pour the liquid ingredients into the bowl with the dry and very gently combine. Be gentle with the batter because you want your muffins to remain light and airy not dense which over mixing will do. It doesn't matter if your batter is lumpy looking - trust me :)
Spoon the batter into your prepared muffin pan. Fill them up to the top, you will get between 10-12 muffins out of this batter.
Pop them in the oven after 5 minutes you need to turn the oven down to 190C / 375F / Gas mark 5. The initial hot temperature will help them to rise then the lower one will bake them throughout without burning them.
Once the time is up check them with a skewer to see if they are fully baked (it should come out clean) if they are take them out of the oven but leave them in their tray for 5 minutes.
After 5 minutes take them out of the muffin pan and place them onto a cooling rack, if you like to eat them warm just give them 10 minutes to cool enough for handling. If you are going to store them allow them to fully cool down.
All muffins are best eaten on the day of baking but they will keep in an airtight tin for 4 days and they freeze well too for up to 3 months.