How to Make It
Heat the oven to 375° F. Stir together the rhubarb, granulated sugar, and potato starch in a large bowl, then transfer to a 9- by 13-inch baking dish. Combine the ground almonds, sliced almonds, and brown sugar in a medium bowl, then stir in the butter and mix well. Sprinkle the almond mixture evenly over the rhubarb. Bake until the topping is golden-brown, about 30 minutes. Let cool for 20 minutes before serving. Serve with ice cream, if desired.