In a large saucepan, bring 1/2 cup sugar and water to a boil. Add the rhubarb. Reduce heat; cover and simmer until tender, about 5 minutes. Combine flour and remaining sugar; stir into rhubarb mixture. Return to a boil; cook and stir until thickened and bubbly, 2 minutes. Stir in butter and almonds. Reduce heat to low; stir occasionally or until butter is melted.
In a large bowl, combine dry ingredients; cut in butter until crumbly. Whisk egg and milk; stir into crumb mixture just until moistened. Pour hot rhubarb mixture into a 2-qt. shallow baking dish. Drop topping into six mounds over the rhubarb mixture.
Bake, uncovered, at 400° until golden brown, 20-25 minutes. If desired, sprinkle cobbler with almonds after removing from oven. Serve warm.