Step 1

Place flour, sugars, butter, and salt into the small bowl of a food processor. Pulse until the mixture resembles coarse crumbs.

Step 2

Add walnuts and pulse until the walnuts are desired size. Set aside.

Step 3

Preheat oven to 425F and line a muffin tin with paper liners.

Step 4

Mix the flour, baking powder, and salt together in a small bowl. Set aside.

Step 5

In the bowl of a stand mixer, cream the butter and sugar together until the mixture becomes pale. Add the eggs one at a time, then add the milk.

Step 6

Gently stir the dry mixture into the wet mixture until it comes together. Do not overmix.

Step 7

Fold in the the walnuts, strawberries, and rhubarb.

Step 8

Evenly distribute the batter in the muffin cups. Top with 1 tbsp of the streusel topping.

Step 9

Bake at 425F for 15 minutes, then check for doneness by inserting a toothpick. If it doesn't come out clean, bake for a few more minutes (no more than 18 minutes).

Step 10

Cool in the muffin tin for 10 minutes, then remove and cool muffins on a wire rack.