Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or line with cupcake liners. Set aside.
Whisk the flour, baking powder, baking soda, and salt together in a large bowl until combined. Set aside.
In a medium bowl, whisk the egg, sugar, and melted butter together until combined. Then whisk in the sour cream, milk, and vanilla extract.
Cut the strawberries and get the chocolate chips ready.
Pour the dry ingredients into the wet ingredients, whisk a few times to begin combining, and then stir with a silicone spatula to finish combining. Batter is very, very thick. Fold in the strawberries and chocolate chips. Avoid over mixing.
Spoon the batter into liners, filling them all the way to the top. Bake for 5 minutes at 425 then, keeping the muffins in the oven, reduce the oven temperature to 350°F (177°C). Bake for an additional 17-19 minutes or until a toothpick inserted in the center comes out clean. The total time these muffins take in the oven is about 22-24 minutes, give or take. (For mini muffins, bake 12-14 minutes at 350°F (177°C) the whole time.)
Allow the muffins to cool for 5 minutes in the muffin pan, and then transfer to a wire rack to continue cooling.
