Preheat the Oven: Preheat the oven to 425°F.
Prepare the Crumb Topping: Combine the brown sugar, cold butter, flour, rolled oats, and cinnamon in a medium bowl. Use your fingers or a fork to cut the cold butter into the dry ingredients until the mixture forms large, coarse crumbles. Work patiently and avoid over-mixing. Set the topping aside. Soak the Oats: Pour the unsweetened vanilla almond milk over the rolled oats and set the mixture aside.
Combine the Dry Ingredients: In a separate bowl, mix the all-purpose flour, vanilla casein protein powder, vanilla whey protein powder, cinnamon, baking powder, baking soda, and salt until evenly combined.
Cream the Butter and Sugar: Using a handheld or stand mixer fitted with a paddle attachment, beat the softened butter and light brown sugar on high speed for about 2 minutes, until the mixture is smooth and creamy.
Add the Eggs: Add the room-temperature eggs one at a time, beating after each addition until well combined.
Incorporate the Coconut Oil: Reduce the mixer speed to low and slowly add the melted coconut oil, mixing until it is thoroughly incorporated.
Combine the Batter: Add the wet ingredients to the dry mixture and mix only until the ingredients are just combined.
Fold in the Blueberries: Gently fold the blueberries into the batter, taking care not to overmix.
Fill the Muffin Cups: Divide the batter evenly among 14 non-stick baking cups.
Add the Crumble: Divide the prepared crumb topping over the muffins, using a spoon or your fingers, then gently press the crumbles into the tops so they adhere to the batter.
Begin Baking: Place the muffins in the 425°F oven and bake for 5 minutes.
Reduce the Oven Temperature: After 5 minutes, lower the oven temperature to 350°F and continue baking for about 20 minutes.
Check for Doneness: Bake until the muffin tops begin to brown slightly and a toothpick inserted into the center of a muffin comes out clean.
