2 cups all-purpose flour
1 cup white sugar
3/4 cup chocolate chips
1/2 cup unsweetened cocoa powder
1 teaspoon baking soda
1 cup plain yogurt
1/2 cup milk
1 teaspoon vanilla extract
1/2 cup vegetable oil
1/4 cup chocolate chips
Preheat oven to 400 degrees F (200 degrees C).
Grease 12 muffin cups or line with paper muffin liners.
Combine flour, sugar, 3/4 cup chocolate chips, cocoa powder, and baking soda in a large bowl.
Whisk egg, yogurt, milk, vanilla, and vegetable oil in another bowl until smooth; pour into chocolate mixture and stir until batter is just blended.
Fill prepared muffin cups 3/4 full and sprinkle with remaining 1/4 cup chocolate chips.
Bake in preheated oven until a toothpick inserted into the center comes out clean, about 20 minutes.
Cool in the pans for 10 minutes before removing to cool completely on a wire rack.