Soft Butter Dinner Rolls

Make the filling:

1. In a stand mixer fitted with the paddle attachment, beat the butter, sugar, and cornstarch until light and fluffy, about 3 minutes. Scoop the dough into 2-teaspoon sized balls and place on a parchment-lined baking sheet. Place in the freezer while you prepare the dough.

Make the dough:

1. Combine the milk, butter, eggs, sugar, and yeast in the bowl of a stand mixer. Add 2 cups of the flour and stir with a wooden spoon until absorbed. Attach the dough hook to the mixer, turn to medium-low speed, and gradually add the remaining flour and salt, kneading until a mass of dough begins to form. Only add as much flour as needed to bring the dough together. Continue kneading on medium-high speed for about 5 minutes or until a soft, smooth ball of dough is formed. The dough should feel elastic and slightly tacky to the touch. Only add additional flour if the dough is unbearably sticky.
2. Lightly spray a large clean bowl with cooking spray and place the dough in the bowl. Cover the bowl lightly with plastic wrap. Let rise for about 1 1/2 to 2 hours at room temperature or until the dough is big, puffy, and about doubled in size.
3. Spray a 13x9-inch baking pan with cooking spray. Gently deflate the dough. Use a bench scraper, knife, or pizza wheel to divide the dough into 15 equal pieces. If you have a digital kitchen scale, weigh the entire mass of dough then divide by 15 to get the perfect portion size for each piece.
4. Flatten a piece of dough and place a ball of the frozen butter on it. Pinch and wrap the dough around the butter and seal completely by pinching hard with your fingers. Roll into a smooth ball. Repeat with remaining dough. Place shaped dough in the prepared baking pan.
5. Lightly cover the dough with plastic wrap and let the rolls rise for 1 hour, or until about doubled in size. If some of the rolls show cracks or splits as they rise, don’t worry. They should bake up just fine.
6. Meanwhile, preheat the oven to 375°F.
7. In a small bowl, whisk together the egg and gently brush over rolls. Sprinkle with sea salt.
8. Bake the rolls for 20 minutes, or until golden brown. Serve warm. Store leftovers in an airtight container or ziptop bag for up to 3 days.