Best Muffin Recipe (also one-bowl!)

Why I Love This Recipe
10 tips for making the very best muffins
1. Start with ingredients at room temperature (including eggs and milk)
2. Take care not to over mix the batter; use a flexible spatula to gently fold ingredients together
3. Batter should be stiff enough to hold a spoon upright; if it seems runny, gently fold in a few extra tablespoons of flour
4. Grease the entire muffin tin, not just the holes.
5. Fill muffin tins 3/4 full -- the fuller the tin, the fuller the muffin top
6. Slide a baking sheet under the muffin tin to prevent the bottoms from getting too dark in the oven
7. Allow muffins to cool in the pan at least 10 minutes before removing them, especially if they contain soft fresh fruit
Ingredients You'll Need
1 c milk
1 tsp white vinegar
1 c rolled oats (not quick oats)
1 large egg, at room temperature
1/4 c dark brown sugar
1/2 c butter, melted and cooled slightly
1 c plus 2 tbsp all-purpose flour
1/4 tsp salt
1 tsp baking powder
1/2 tsp baking soda
1/4 tsp nutmeg
1/2 tsp cinnamon
whatever add-ins you may want
Favorite combinations:
1 c raspberries, fresh or frozen & 1/2 c dark chocolate, chunked or chips
3/4 c diced apple (granny smith or russet), and 1/2 c toasted walnuts, roughly chopped
3/4 c dried cranberries and 1/2 c toasted pecans, roughly chopped
1/2 c toasted unsweetened coconut & 3/4 c PB chips
1 c diced rhubarb, fresh or frozen & 1/2 tsp green cardamom
3/4 c dates, pitted and chopped & 1/2 c pistachios
3/4 c golden raisins & 3/4 c grated carrot
Directions
Preheat the oven to 375F. Grease a 12-cup muffin tin and line with cupcake papers.
Crack the egg into the oat and milk mixture
Add brown sugar and mix to combine
Stir in melted butter
Sift remaining ingredients into the bowl: flour, salt, baking powder, baking soda & spices
Gently fold into batter, taking care not to over-mix
Sprinkle add-in and flavorings of your choice and combine muffin batter gently.
Use a large ice cream scoop or 1/3c measuring cup to scoop batter into muffin tins.
Bake until light brown and tops spring back gently touched, about 10-12 minutes
Note: muffins will take slightly longer to bake if you are adding fresh fruit
Remove from oven and cool in tins. To remove, run a sharp knife around the edges and pop muffins out.
* You may substitute 1c buttermilk, and then omit the vinegar from the recipe
* You can freeze the batter, then thaw in refrigerator overnight to bake fresh in the morning