Combine all streusel ingredients in a small mixing bowl with a pastry blender or fork.. When it is well mixed, work the mixture between your fingers until it begins to hold together. Set aside.
Preheat oven to 375 F degrees. Line a 12 cup muffin pan with cupcake liners.
In large bowl beat eggs with an electric hand mixer. Add 1 cup white sugar and beat for a minute or two until completely combined. Pour in the oil, with beaters running, and then add vanilla. In a separate bowl, stir together flour, cinnamon, nutmeg, salt and baking soda.
Using a wooden spoon, mix flour mixture into wet mixture, a little at a time, alternating with the sour cream (or Greek yogurt).
Add the chopped apple and mix with the wooden spoon just until combined. Divide the batter between cupcake liners. Divide streusel topping evenly over the muffin tops, pressing down lightly into the batter. Brush off as much of the streuself from the area between muffins for easier cleanup.
Bake in preheated oven for 22 to 25 minutes, or until a toothpick inserted in center of muffin comes out clean. Remove from oven and allow muffins to cool for about 10 or 15 minutes and then carefully remove from muffin pan to cool completely.
Whisk together glaze ingredients and drizzle over completely cooled mufins.
Store leftovers in an airtight container.