Pre-heat oven to 325 F. In the bowl of a stand mixer, combine butter and sugar on low gear. Meanwhile, in a separate bowl, combine ¾ C flour, baking soda, powder and salt. Set aside. To the butter/sugar mixture add egg and vanilla. Add dry ingredients and continue mixing until just combined, then add the sour cream. In a small bowl, toss frozen blueberries with remaining ¼ cup flour and using a spatula, gently fold into batter. Note: Please refer to the written recipe for measurements as they've been adjusted from the video.
Make the streusel by combining the flour, sugar, almond flour and salt in the bowl of a food processor, then add the diced, cold butter, mixing until it there aren’t pieces of butter. Set aside. Using an ice cream scoop, distribute batter into a 12-cup standard muffin tin with liners. If the batter is sticking to the scoop, dip in water. Sprinkle a teaspoon of streusel mixture on each muffin. Bake 25 minutes until muffins are puffed and golden brown. Note: Please refer to the written recipe for measurements as they've been adjusted from the video.
Check for "doneness" by sticking a knife into the center of a muffin. It should come out clean. When cool, finish with a sprinkle of powdered sugar.