Preheat the oven to 400 degrees Fahrenheit and line a muffin tin with cupcake liners. Set aside.
In a large mixing bowl, beat together the sugar, peanut butter, oil and egg with an electric mixer (hand held or stand up).
Add the milk and vanilla extract. Mix until combined.
Stir the peanut butter mixture into the flour mixture and gently stir until just combined. Be careful not to over mix.
Pour the batter evenly into the muffin tin filling them up approximately ¾ of the way full.
Bake for 15-18 minutes until the center of the muffins are set and a toothpick inserted into the center of the muffins comes out clean.
Let the muffins cool in the pan for 10-15 minutes and then move to a wire rack to cool completely.
Then the muffins are ready to serve and enjoy!
