Place 2 large eggs and 1 ¼ cups buttermilk on the counter and let come to room temperature.

Arrange a rack in the middle of the oven and heat the oven to 375°F. Coat the wells of a standard 12-well muffin pan with cooking spray or line with paper liners.

Cut 1 stick unsalted butter into 8 pieces and place in a large microwave-safe bowl. Microwave in 20-second bursts until mostly melted, 40 to 60 seconds total. Set aside to let the butter finish melting and cool slightly. (Alternatively, melt the butter on the stovetop, then pour into a large bowl.)

Add the eggs, buttermilk, 1 cup of the granulated sugar, 2 tablespoons neutral oil, 1 tablespoon vanilla extract, and ½ teaspoon kosher salt to the butter. Whisk until combined.

Sprinkle 1 tablespoon baking powder and ½ teaspoon baking soda evenly over the top. Add 2 ½ cups all-purpose flour and stir with a flexible spatula until just incorporated. Add 1 cup semi-sweet chocolate chips and fold until just combined, but do not overmix. Let the batter rest at room temperature until slightly puffed, about 5 minutes.

Divide the batter among the muffin wells (about ⅓ cup per well). Sprinkle the top of each muffin with ½ teaspoon granulated sugar.

Bake until the muffins are golden-brown, the tops bounce back when pressed, and a toothpick inserted in the center of a muffin comes out clean, 23 to 25 minutes. Let the muffins cool in the pan for 5 minutes, then transfer to a wire rack and let cool completely.