Preheat the oven to 375°F. Spray a 12-cup muffin tin with nonstick spray, or line the cups with paper liners, and spray those with nonstick spray.
Place the butter in a small saucepan over medium heat. Melt the butter, stirring occasionally, and allow it to get medium brown; not too dark, but deeper than golden. It should smell toasty and nutty. Set aside to cool.
Make the streusel: in a medium bowl combine the sugar, brown sugar, flour, cinnamon, cloves, ginger and salt. Stir in the walnuts if using. Add the chilled butter and use your fingers to rub the butter into the dry ingredients until the mixture is coarsely crumbly. Set aside in a cool place.
In a medium bowl toss the apples with the lemon juice. Set aside. In a medium bowl combine the flour, sugar, baking powder, salt and cinnamon.
In a large bowl mix together the cooled browned butter, eggs, milk or yogurt, and vanilla. Add the dry ingredients to the bowl in two batches, stirring each batch into the wet mixture just until incorporated; you should still see a few streaks of flour. Fold in the apples, just until they are incorporated; do not overmix.
Use a spoon or ice cream scoop to fill the prepared muffin tins ¾ full. Evenly distribute the streusel over the tops of the batter.
Bake for 22 to 25 minutes, until a wooden skewer or toothpick inserted into the center of a muffin comes out clean, or with just a crumb or two clinging to it.
Cool in the tin on a wire rack for 10 minutes, then turn the muffins out of the tin and finish cooling on the rack. Serve warm or at room temperature.
Notes
If you don’t have the ground cloves or ginger, the cinnamon will be enough to give the muffins that wonderful autumnal flavor.