Preheat the oven to 400 F degrees and line standard muffin pan with paper liners and set aside.
To make the crumb topping in a small bowl, whisk together flour, sugar, brown sugar and cinnamon, add melted butter and stir with a fork until crumbly and set in the fridge until ready to use.
To make the muffins in a large bowl stir together flour, baking powder, salt, cinnamon and nutmeg, then set aside.
In a medium bowl, whisk together eggs and granulated sugar until combined. Whisk in Greek yogurt, oil, and vanilla extract (mixture should be pale yellow)
Fold wet ingredients into dry ingredients and mix everything together by hand. The batter will be quite thick.
Spoon batter into prepared muffin tins, filling less than 2/3 of each cup. Tap the pan onto working surface to set the batter, then add heaping Tablespoon of chopped apples in each cup and gently press the apples into the batter. Top generously with streusel topping.
Place them in the oven and reduce the heat to 375F, bake about 19-22 minutes or until the toothpick inserted in the center comes out clean.
Cool for 5 minutes in the pan then remove muffins and cool on a wire rack.
To make the glaze stir together powdered sugar and milk. If it’s too thin add more powdered sugar, if it’s too thick add more milk. Drizzle over cooled muffins.