1Heat oven to 375°F. Stir together Bisquick mix, milk, 3 tablespoons sugar and the butter in medium bowl. Spread in ungreased square pan, 9x9x2 inches. Arrange peach slices on top.
2Mix 1/4 cup sugar and the cinnamon; sprinkle over peaches. Mix sour cream and egg; drizzle over top.
3Bake 35 to 40 minutes or until toothpick inserted in cake comes out clean. Serve warm with whipped cream.