Small Batch Blueberry Muffins with Crumb Topping

Ingredients

• 1/4 cup unsalted butter, melted
• 1/2 cup granulated sugar
• 1 egg
• 2 tbsp greek yogurt
• 1/4 cup milk
• 1/2 teaspoon vanilla extract
• 1 cup + 1 tbsp all purpose flour
• 1 1/2 tsp baking powder
• 1/4 teaspoon salt
• 1 cup blueberries, fresh or frozen
• 1 tbsp unsalted butter, melted
• 2 tbsp granulated sugar
• 2 tbsp all purpose flour