In a medium bowl, whisk together the flour, baking soda, and salt. Set this aside.

In a large bowl, using a hand mixer or stand mixer, beat the softened butter, granulated sugar, and brown sugar together until light and fluffy, about 2-3 minutes.

Add the peanut butter and mix until just combined. Then, add the eggs one at a time, beating well after each addition.

Mix in the sour cream and milk. Don’t worry if the batter looks a little curdled at this stage; that's perfectly normal!

Gradually add the dry ingredients to the wet ingredients. Mix on low speed only until the flour is just incorporated. Be careful not to overmix the batter; a few lumps are okay. Overmixing can lead to tough muffins.

Gently fold in the chocolate chips with a spatula.

Divide the batter evenly among the prepared muffin cups, filling each one about three-quarters full. If you like, sprinkle a few extra chocolate chips on top of each muffin.

Bake for 18-20 minutes, or until a wooden skewer inserted into the center of a muffin comes out clean or with moist crumbs attached.

Let the muffins cool in the pan for a few minutes before transferring them to a wire rack to cool completely.