Make the streusel: Whisk together the sugar, flour, cinnamon and a pinch of fine sea salt. Slice the softened butter and add it to the bowl. Work the butter into the flour with your fingers, rubbing it in to coat the flour. Once your butter bits are fully mixed in, add the oats and mix in with your fingers. The goal is to have this clump, the more you work the butter in and squeeze the streusel the bigger your crumbles will be. Set aside while you make the batter.

Make the muffins: add the butter, sugar, vanilla, spices, and salt and use a hand mixer to beat until the mix is light and somewhat airy. This will take a few minutes and you may need to scrape down the bowl a few times to ensure even mixing. Add the eggs and beat until smooth, the mix will be a few shades lighter. Add the flour, baking soda, baking powder and buttermilk to the bowl and beat just a bit - until it’s halfway combined. Shred the apple and add it to the bowl along with the rolled oats. Now beat until fully combined and stop as soon as it is.

Top & Bake: Preheat the oven to 425 F. Line two cupcake/muffin tins with parchment cupcake liners so that no two muffins will bake next to each other (so every other one). Fill each muffin cup with batter so it’s almost full. Add the crumble on top, squeezing it so it is in bigger bits as you pick it up from the bowl and dot it over the muffin batter. Bake the muffins for 7 minutes at 425 F then lower the temperature to 350 F and bake until the tops spring back when pressed or a cake tester comes out clean.