In a medium bowl, combine all-purpose flour and light brown sugar. Blend in softened unsalted butter until the mixture resembles coarse crumbs.

In a large mixing bowl, whisk together granulated sugar, orange zest, sifted all-purpose flour, baking powder, baking soda, and salt.

In a separate bowl, blend together the eggs, Greek yogurt, melted unsalted butter, milk, and optional vanilla extract until smooth.

Make a well in the center of the dry ingredients and pour the wet mixture into this well. Fold until just combined.

Toss the fresh strawberries lightly in flour, then fold gently into the batter.

Preheat your oven to 400°F (200°C) and line a muffin pan with paper liners.

Spoon the batter into the prepared muffin liners, filling each about two-thirds full and sprinkle the streusel topping on each.

Bake at 400°F for 10 minutes, then reduce temperature to 350°F and bake for an additional 15 minutes.