You can use frozen berries but do not thaw them and use closer to the 3 tablespoons of cornstarch.
Make your own buttermilk by mixing together a scant 1/2 cup of milk with 1 1/2 teaspoons of lemon juice or white vinegar. Let it sit for 5 minutes, and then add it to the flour-butter mixture to make the dough.
You don’t have to brush on the egg wash, but I strongly suggest it since it helps brown the dough well. Appearance is important.
Let the cobbler sit for a bit before dishing it out. It stays hot for quite a while. It will thicken as it cools, and if you serve it while it is too hot, the scoop of ice cream or the whipped cream will not hold up long enough to get seated with your dessert.
Store leftovers in an airtight container in the refrigerator for up to 3 days.
Freeze the baked berry cobbler for up to 1 month. Let it cool completely before covering it with 2 layers of plastic wrap. Place on a level shelf in the freezer. Thaw in the refrigerator overnight.
Nutrition
Calories: 313kcal | Carbohydrates: 52g | Protein: 3g | Fat: 11g | Saturated Fat: 6g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 3g | Trans Fat: 0.4g | Cholesterol: 42mg | Sodium: 274mg | Potassium: 114mg | Fiber: 4g | Sugar: 32g | Vitamin A: 384IU | Vitamin C: 3mg | Calcium: 68mg | Iron: 1mg