1
Melt the butter in a skillet over medium heat.
2
Add the peaches, brown sugar, cinnamon, vanilla, and lemon juice (if using).
3
Cook for 5–8 minutes, stirring occasionally, until the peaches are softened.
4
In a small bowl, whisk together the cornstarch and water.
5
Stir the slurry into the peaches and cook for 1 minute, stirring constantly, until slightly thickened.
6
Remove from the heat and allow the filling to cool completely before folding into the batter.
7
Mix all ingredients together with a fork until coarse crumbs form.
8
Refrigerate while preparing the muffin batter.
9
Preheat oven to 425°F and line a 12-cup muffin pan with paper liners.
10
In a large bowl, whisk together the melted butter and sugar until combined.
11
Add the eggs one at a time, mixing well after each addition.
12
Stir in the vanilla, sour cream, and milk until smooth.
13
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
14
Gently fold the dry ingredients into the wet ingredients just until combined. Do not overmix.
15
Fold in 2–3 tablespoons of the cooled peach filling (or floured fresh peaches).
16
Divide the batter evenly between the muffin liners, filling each nearly to the top for tall bakery-style muffins.
17
Spoon a little extra peach filling onto the tops, if desired, then generously sprinkle with the crumble topping.
18
Bake at 425°F for 5 minutes.
19
Without opening the oven, reduce the temperature to 350°F and continue baking for 15–20 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean or with a few moist crumbs.
20
Let the muffins cool in the pan for 5 minutes before transferring to a wire rack.
21
Whisk together until smooth, then drizzle over slightly warm or completely cooled muffins.