Spray 18 wells of two 12-count muffin pans with non-stick spray or line the wells with cupcake liners. Set aside.
STREUSEL
Place flour, butter, brown sugar, and salt into a small bowl.
Using a fork, press ingredients together until butter is in small chunks. Use your fingers to pinch pieces together until streusel is mostly small crumbles. Some large crumbles are ok. Stir in sliced almonds. Set aside in the refrigerator.
MUFFINS
In a large bowl, toss together the flour, baking powder, baking soda, and salt. Set aside.
In a medium size bowl, whisk together the brown sugar, granulated sugar, and butter until smooth. Add the eggs, buttermilk, and almond extract and whisk again until everything is combined.
Pour the wet ingredients into the dry ingredients and stir gently with a spatula until just combined. Fold in the diced peaches.
Spoon batter equally into prepared muffin pans. Add crumble to the top of each muffin, about 2-3 Tablespoons each. Bake muffins for 5 minutes, then reduce heat to 350ºF and bake for an additional 13-15 minutes until streusel starts to brown and a toothpick inserted in the center comes out mostly clean. Remove from oven and allow to cool completely on a wire rack. Muffins will stay fresh in an airtight container at room temperature up to 3 days or in the refrigerator up to one week. Muffins freeze well, up to 2 months. Thaw in microwave for 45-60 seconds before eating.
Notes
It is always a good rule of thumb to use room temperature eggs when using room temperature butter. To bring eggs to room temperature quickly, place in a bowl of warm water for 10 minutes.
If you don't have buttermilk, you can easily make your own: see my post about how to make your own buttermilk.
Equivalent of about 3 peaches. If using frozen peaches, do not thaw.
All nutritional values are approximate and provided to the reader as a courtesy. Changing ingredients and/or quantities will alter the estimated nutritional calculations.