Preheat the oven to 350°F/180°C/Gas 4. Line cupcake pans with 14 cupcake liners and set aside.

To make the crumble topping, place the flour, sugar, and cinnamon into a medium bowl and whisk to combine. Add the butter, and using a fork, pastry blender, or your fingers, cut the butter into the dry ingredients to make a crumble texture. Set aside.

To make the cupcakes, sift or whisk the flour, baking powder, cinnamon, and salt into a medium bowl and set it aside.

Using an electric handheld or standing mixer, combine the butter and sugar until light and fluffy. Beat in the eggs one at a time and the vanilla extract until combined.

Alternating with the milk, beat the flour mixture into the wet mixture until combined and smooth.

Spoon half a tablespoon of the crumble mixture into the bottom of each cupcake liner. Use an ice cream scoop to transfer the cupcake batter to each liner, filling them about ¾ way full.

Bake the cupcakes in the oven for about 20 minutes or until a toothpick inserted into the center of a cupcake comes out clean. Remove from oven and cool in the pan for 5 minutes before transferring them to a wire rack to cool completely before decorating.

To make the cinnamon frosting, use an electric handheld or standing mixer to beat the butter, powdered sugar, vanilla, cinnamon, and heavy whipping cream until combined, smooth, and holds a peak. Scoop the frosting into a large piping bag fitted with a large star tip. Set it aside.

To make the glaze, combine all ingredients in a small bowl and whisk until smooth. Transfer into a disposable piping bag - do not cut off the tip yet.

Pipe a thick ring of frosting around the top of each cooked and cooled cupcake, and coat the frosting into the remaining crumble to cover completely. Pipe a swirl of frosting into the center of the crumble layer. Place a mini doughnut on top.

Cut the tip off the disposable piping bag and drizzle the glaze over the top of the cupcake. Serve and enjoy!