Put the flour, brown sugar, vanilla extract, spices and salt in food processor bowl. Add the butter cut in several small pieces and scatter in bowl.
2Pulse several times and keep pulsing until the mixture looks like a loose crumble and you can press some of the mixture together with your fingers to make clumps. (do not over mix or it becomes clumpy..still tastes good just doesn't look as good)
3MUFFIN: Preheat oven to 375 degrees.
4In a bowl, sift flour, baking powder, and baking soda (do not skip this step); reserving 1/4 cup of flour mixture for coating the berry's later. Set dry ingredients aside.
5In a 2 cup measuring cup or small bowl combine sour cream, buttermilk, vanilla extract, nutmeg, and salt. Set wet ingredients aside.
6Using an electric stand mixer equipped with paddle; combine the butter, and sugar and mix on medium speed 2-3 minutes; until mixture is pale and well whipped. Scrape sides about half way through mixing.
7Turn mixer to medium speed and add eggs one at a time, mixing well between eggs.
8Add the wet and dry mixture you set aside to egg mixture in 3 additions. MIX ONLY UNTIL BLENDED.
9Put berries in a small bowl and toss with 1/4 reserved dry ingredients to coat berries.
10Gently fold berry's into batter.
11Scoop batter into 12 paper lined muffin cups using an ice cream scoop or 1/3 cup measure.
12Top with streusel and bake until golden and baked through, about 23-25 minutes. Rotate pan half way through baking. Check with toothpick.
13Remove from oven and cool on cooling rack 10 minutes before removing muffins from the pan.