Coffee Cake Muffins

Ingredients

• 1/3 cup (40 grams) light brown sugar
• 1/3 cup (35 grams) all-purpose flour
• 1/4 cup (25 grams) rolled oats
• 1/4 teaspoon ground cinnamon
• 1/4 teaspoon kosher salt
• 4 tablespoons (1/2 stick) cold unsalted butter, cut into small cubes
• 1/3 cup chopped pecans or walnuts (optional)
• 1/2 cup (1 stick) unsalted butter, room temperature, plus more for the pans
• 3/4 cup (90 grams) all-purpose flour
• 3/4 cup (90 grams) whole-wheat pastry flour
• 2 teaspoons baking powder
• 1 teaspoon ground cinnamon
• 1/2 teaspoon ground ginger
• 1/2 teaspoon ground cardamom
• 3/4 teaspoon kosher salt
• 1/2 cup (100 grams) granulated sugar
• 3/4 cup plain full-fat yogurt or sour cream
• 1 teaspoon vanilla extract
• 2 large eggs
• 1/4 cup powdered sugar
• 1 1/2 teaspoons milk