Preheat oven to 350 degrees and line or grease muffin tins.
In a saucepan over medium heat, melt butter. Swirl as it starts to brown until it reaches a nutty aroma and is slightly brown in color. Remove from heat . Allow to cool 5 minutes.
In a mixing bowl, combine sugar, brown butter and oil. Add egg, egg white, vanilla and buttermilk until just combined.
In a separate bowl, combine flour, baking powder, cornstarch and salt. Gradually fold into wet mixture until just incorporated. Do not over mix.
Fill muffin tins with liners and pour batter into tin just below the top of the liner.
Bake 22 minutes or until a toothpick comes out clean.
Notes
Substitutions and Variations
Butter - Salted or unsalted, your preference.
Oil - Vegetable oil works best, but you can substitute canola oil.
Vanilla - You can also use Almond Extract or Rum.
Buttermilk - No buttermilk, no problem. Simply combine a 1/2 cup milk with 1 1/2 teaspoons lemon juice and allow to sit 10 minutes before incorporating into the recipe.
Optional
Nuts - Pecans, walnuts, or almonds.
Fruits - The options are endless, strawberries, blueberries, raspberries, cranberries, blackberries, lemon or orange zest.
Crumb Topping - Combine 1 tablespoon softened butter softened, 1/3 cup packed brown sugar, a 1/2 teaspoon cinnamon and 2 tablespoons flour. Sprinkle on just before baking.
Donut Muffins - Turn them into donut muffins by dipping them in melted butter, followed by cinnamon and sugar. Just melt 1/4 cup butter in a shallow bowl. Combine 1/2 cup sugar with 1 teaspoon cinnamon.
Tips
Larger Muffin Tops - or larger muffin tops, allow batter to rest 10 minutes before baking.
Toothpick Test - Muffins are done when a toothpick inserted into the center of the center muffin comes out clean.
Baking Alternatives
Mini Muffins - Fill your traditional muffin pan 2/3 of the way full. Bake at 350 for 12 minutes.
Loaf - Fill a greased loaf pan and bake at 350 degrees for 50-60 minutes or until a toothpick comes out clean.
To Store
Refrigerate – Allow them to cool in the tin for a few minutes and transfer to a wire rack. Store in an airtight container or ziplock bag on a paper towel to absorb any excess moisture.
Freeze - Wrap muffins in saran wrap and place them in a freezer bag to store up to 3 months.
To thaw, bring to room temperature (about 3-4 hours)
To warm, preheat oven to 350 degrees and bake 3 minutes