• Preheat oven to 350 degrees F. Prepare a 9-10 inch angel food tube pan with removable bottom with non-stick spray. NOTE: Use a pan with a removable centerpiece for easy removal of the cake.
• In a large bowl, whisk together the melted butter, sugar, sour cream and eggs. Set aside.
• In a medium bowl, whisk together the 3 cups flour, baking powder, baking soda and salt. Slowly add the dry ingredients into the wet and keep mixing until just combined.
• Coat the blueberries with the 1 teaspoon of flour and then gently fold them into the batter. NOTE: The batter will be thick so take care not to smash the blueberries into the batter.
• Spoon the batter into the prepared pan and evenly spread it out.

Crumble Topping

• Mix together using a fork the unsalted butter (4 TB), flour (1/2 cup), brown sugar (1/2 cup), cinnamon (1 teaspoon) and salt (1/2 teaspoon). The mixture should be crumbly.
• Sprinkle it evenly over the batter.

Baking and Cooling

• Bake for 55-60 minutes, until a toothpick comes out clean. Place on a cooling rack for 10 minutes. When cool enough to be handled, remove from the pan to cool fully on the cooling rack.
• When fully cooled, place the cooling rack on a foil-lined rimmed baking sheet underneath.

Glazing the Coffee Cake

• Prepare the glaze by mixing the 1/2 cup of powdered sugar with 2 tablespoons of milk, then slowly add more milk and keep mixing until the desired consistency has been reached.
• Pour the glaze all over the top. NOTE: excess glaze will drip down into the baking sheet below. When the glaze has hardened slightly, remove the foil from the baking sheet and discard.
• Slice and enjoy your cake for breakfast! Store covered at room temperature.