Preheat the oven to 425°F (220°C). Line two standard 12-cup muffin pans with 6 paper liners each, filling every other well to encourage taller muffin tops. If you only have one muffin pan, bake all 12 muffins together. The muffins will still turn out well, but the tops may not rise quite as high.
Place the butter in a small saucepan over medium heat. Cook until it melts, foams, and the milk solids turn deep golden brown, swirling the pan occasionally. As soon as the butter smells nutty and you see browned bits on the bottom of the pan, pour it into a heatproof bowl to stop the cooking. Let cool for 10 to 15 minutes.
¼ cup (57 g) unsalted butter
While the butter cools, stir together the streusel flour, brown sugar, cinnamon, and salt in a small bowl. Pour in the melted butter and mix with a fork until large crumbs form. Refrigerate until ready to use.
½ cup (60 g) all-purpose flour, ⅓ cup (67 g) light brown sugar, ½ tsp (1 g) ground cinnamon, pinch of salt, 4 tbsps (57 g) unsalted butter
Wash, dry, and dice the peaches into small bite-sized pieces. Pat them dry if they're especially juicy, then toss with 1 teaspoon (3 g) all-purpose flour to absorb excess surface moisture and help keep the peaches evenly distributed throughout the batter.
1¼ cups (190 g) diced fresh peaches , 1 tsp (3 g) all-purpose flour
In a large bowl, whisk together the cooled brown butter, vegetable oil, eggs, granulated sugar, and salt until smooth. Whisk in the Greek yogurt, vanilla extract, and almond extract, if using.
¼ cup (60 ml) vegetable oil, 2 large eggs, ¾ cup (150 g) granulated sugar, ½ tsp (3 g) table salt, 1 cup (245 g) full-fat Greek yogurt, 1 tsp (5 ml) vanilla extract, ¼ tsp (1 ml) almond extract
Add the flour, baking powder, baking soda, and cinnamon. Fold gently with a rubber spatula just until a few streaks of flour remain. Avoid overmixing, which can make the muffins dense. Fold in the peaches until evenly distributed. The batter will be thick.
2 cups (240 g) all-purpose flour, 2 tsps ( 8 g) baking powder, ½ tsp (3 g) baking soda, ½ tsp (1 g) ground cinnamon
Divide the batter evenly among the prepared muffin liners, filling each almost to the top. Generously sprinkle the streusel over each muffin, gently pressing a few of the larger crumbs into the batter so they stay in place while baking. Finish with a sprinkle of coarse sugar.
coarse white sugar
Bake for 5 minutes at 425°F (220°C). Without opening the oven door, reduce the oven temperature to 350°F (175°C) and continue baking for 15 to 18 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs attached.
Let the muffins cool in the pan for 5 to 10 minutes, then transfer them to a wire rack.
Once the muffins have cooled for 15 to 20 minutes, whisk together the confectioners' sugar, heavy cream, and vanilla extract until smooth. Drizzle over the muffins. Waiting until they've cooled slightly helps the glaze stay on top instead of soaking into the streusel.
1 cup (120 g) confectioners' sugar, 3 tbsps (45 ml) heavy cream, ½ tsp (2.5 ml) vanilla extract