Place the Unsalted Butter (1/2 cup), All-Purpose Flour (3/4 cup), and Granulated Sugar (3/4 cup) into a bowl.
Use your fingers or a large fork to rub the mixture together until the mixture resembles streusel. Set aside.
Preheat oven to 350 degrees F (176 degrees C) and grease a 12 cup muffin tin.
Whisk together the All-Purpose Flour (2 cup), Baking Powder (2 teaspoon) and Salt (1/2 teaspoon). Set aside.
In a separate bowl, whisk together the Milk (3/4 cup), Vegetable Oil (1/4 cup), Egg (1), Granulated Sugar (8 tablespoon) and Pure Vanilla Extract (2 teaspoon).
Mix in by hand the dry ingredients just until the batter comes together. Add the Fresh Strawberry (1 cup) and Rhubarb (1 cup).
Divide the batter evenly among the 12 cups in a muffin tin. Sprinkle the streusel on top.
Bake for 20 minutes or until a knife inserted comes out clean.
Transfer to a wire rack to cool. Lovely if served slightly warm.