Crumb Topping

• 1/4 cup sugar
• 1/4 cup light brown sugar
• 1/3 cup rolled oats
• 1/3 cup flour
• 1/4 tsp cinnamon
• pinch of salt
• 1/4 cup unsalted butter

Muffins

• 1 1/2 cups flour
• 3/4 cup sugar
• 1/4 cup light brown sugar
• 1 tsp baking powder
• 1 tsp baking soda
• 1 tsp cinnamon
• 1/4 tsp ginger
• 1/8 tsp cloves
• 1/8 tsp nutmeg
• 1/2 tsp salt
• 2/3 cup low-fat buttermilk, at room temperature
• 1/2 cup plain fat-free Greek yogurt, at room temperature
• 1/4 cup unsalted butter, melted and slightly cooled
• 1 large egg, lightly beaten
• 2 tsp vanilla extract
• 1 1/4 cups apple, peeled and finely chopped

Glaze

• 1 Tbsp unsalted butter, melted
• pinch of salt
• 1 tsp vanilla extract
• 3/4 cup powdered sugar, sifted
• 1 1/2 Tbsp milk