Big Apple Crumble Cupcakes

Preheat the oven to 350°F.
In a medium mixing bowl, combine all of the ingredients, and mix together using your fingertips. Spread the crumb mixture on a cookie sheet lined with parchment paper, and bake for 30 minutes or until the crumble reaches a golden brown color. Let cool and set aside. Leave the oven on to bake the cupcakes.
Line a cupcake pan with twelve paper baking cups and a second pan with six baking cups.
Sift together the flour, baking powder, cinnamon, and salt, and set aside.
In the bowl of a stand mixer or in a bowl with a handheld electric mixer, cream together the butter and sugar until light and fluffy, approximately 3 to 5 minutes.
Add the eggs one at a time, mixing slowly after each addition.
Add one third of the flour mixture to the butter mixture, then gradually add one third of the hot water, beating slowly until well incorporated. Add another third of the flour mixture, followed by a third of the hot water. Add the remaining flour mixture, followed by the remaining hot water, and beat just until combined. Stop to scrape down the bowl as needed.
Using a spatula, fold the grated apple and half of the apple crumble mixture into the batter.
Using a standard-size ice cream scoop, fill each baking cup so that it is two-thirds full. Bake for 18 to 20 minutes (start checking at 15 minutes) or until a toothpick inserted into the center of a cupcake comes out clean. After 5 minutes, transfer the cupcakes to a wire rack to cool completely for approximately 20 minutes.
Place all ingredients in the bowl of a stand mixer or in a bowl with a handheld electric mixer. Beat until the frosting is light and airy, approximately 3 to 5 minutes. Frost each cupcake with a signature swirl (see below), and top with a sprinkling of the remaining apple crumble.