Preheat oven to 350 degrees.
Butter a 9x5-inch loaf pan - or spray with baking spray, and set aside.
In a medium size mixing bowl combine the chopped apple, brown sugar, cornstarch, and cinnamon.
Toss to evenly coat the apples, set aside.
In the bowl of a stand mixer, mix the flour, sugar, baking powder, salt, and nutmeg on low.
With mixing speed on low, gradually add the butter one tablespoon at a time.
Continue mixing until crumbs form, about 2 minutes.
Add the eggs, vanilla, sour cream and milk.
Beat on medium-high speed until light and fluffy, about 1-2 minutes, scraping the bottom of the bowl half way through.
Pour half of the batter into the prepared pan.
Add half the apples mixture. Lightly pat the apples into the batter.
Pour the remaining batter over top, then the remaining apples.
Use a knife to swirl it together a bit.
Place in oven and bake for 45-60 minutes, or until the center is set.
Baking time will vary, so watch it at the 45 minute mark & test for doneness.
Remove from the oven and allow the bread to cool for 30 minutes in the pan before removing.
To prepare the glaze, whisk together the powdered sugar, half-and-half, and maple extract.
Add more half-and-half or powdered sugar to reach desired consistency.
Drizzle glaze over bread, allow 15 minutes for the glaze to firm up.