Start by preheating your oven to 350°F (175°C). This ensures that your muffins will bake evenly.
Grease your muffin tin with a little butter or line with paper liners to prevent sticking.
In a large mixing bowl, cream together the room temperature butter and sugar until light and fluffy. This should take about 2-3 minutes with a whisk or an electric mixer.
Add the eggs one at a time, mixing well after each addition. Then, stir in the peanut butter until fully combined.
Pour in the milk and mix until the batter is smooth.
In another bowl, whisk together the all-purpose flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, stirring just until combined. Be careful not to overmix; a few lumps are okay!
Gently fold in the peanut butter chips until evenly distributed throughout the batter.
Scoop the batter into the prepared muffin tin, filling each cup about two-thirds full.
Place the muffin tin in the preheated oven and bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Once baked, allow the muffins to cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely. Enjoy your Easy Peanut Butter Muffins warm or at room temperature!