In a medium bowl, combine 2 c. flour, baking powder and cinnamon. Set aside.
Beat 1/4 c. milk, ¾ c. brown sugar, 1/2 c. sour cream, ¼ c. butter, egg, and vanilla until creamy. Add dry ingredients and mix just until blended.
Fold in peaches.
Spoon batter into a 10 inch springform pan and sprinkle with crumble topping (see below).
Bake at 350 degrees for 50-55 minutes or until center is set and top is golden brown.
Combine ingredients for glaze and drizzle over baked coffee cake.