1 stick (4 ounces) unsalted butter, melted and cooled
1 1/2 cups fresh or frozen cranberries
1 cup confectioners' sugar
1 1/2 tablespoons water
MAKE THE GLAZE
Preheat the oven to 425°. Lightly grease the cups and top of a 12-cup nonstick muffin pan.
In a pie plate, toast the walnuts for 5 minutes, or until browned and fragrant; cool. In a large bowl, mix the flour with the granulated and light brown sugars, baking powder and salt. Stir in the butter, then add the walnuts and pinch the topping mixture into clumps.
In a medium bowl, mix the flour with 1/2 cup of sugar, baking powder, baking soda and salt. In another bowl, mix the yogurt with the egg and butter; stir in the dry ingredients. Toss the cranberries with the remaining 1 1/2 tablespoons of sugar and fold into the muffin batter.
Spoon the batter into the muffin cups and cover with the crumb topping. Gently press the topping onto the muffins so it adheres. Bake for 20 minutes, or until the muffins are golden and a toothpick inserted in the center comes out clean. Let the muffins cool in the pan for 5 minutes, then transfer to a rack set over a baking sheet.
In a medium bowl, mix the confectioners' sugar with the water until smooth and barely runny. Drizzle the glaze over the warm muffins and let it set. Serve the muffins warm or at room temperature.