Preheat oven to 375 degrees F. Line two muffin tins with cupcake liners. Set aside.
In a medium bowl, stir together flour, baking powder, and salt. Set aside.
In a large mixing bowl, beat together butter and sugar until pale and fluffy, about 1 minute. Add eggs, one at a time, mixing after each addition. Add vanilla and mix until combined. Scrap the sides of the bowl as needed.
Add 1/2 the dry ingredients to the wet ingredients. Mix until just combined. Pour in the Shamrock Farms whole milk and mix to incorporate. Add the other half of the dry ingredients and mix until combined.
Use a rubber spatula or wooden spoon to mix in the blueberries by hand.
Portion the batter into prepared muffins tins, filling each cup about 2/3 full. (I like to use a medium-sized cookie scoop for this.)
In a medium bowl, stir together flour, sugar, and cinnamon for streusel. Use a fork to cut in the butter. You want to work quickly so the butter doesn't get too soft. When the butter is incorporated, you should have a crumbly sand texture.
Sprinkle streusel over the tops of the muffins, as much or as little as you like.
Bake muffins for 25 to 30 minutes, or until a toothpick inserted in the center comes out clean.
Remove muffin tins from oven. Allow muffins to cool in pan for 5 minutes before transferring to a wire rack to cool completely. Serve warm or at room temperature.
Notes
If blueberries aren't in season, you can substitute 1 1/2 cups frozen blueberries. Do not thaw the blueberries first or they will bleed into your muffin color turning them blue/purple.