Crunch: * 1 lb rhubarb; (about 5 cups) * 1 1/4 c Sugar, granulated * 1/2 c flour * 1/2 ts cinnamon, ground * 3/4 c orange juice Topping: * 1/2 c flour * 1/2 c oatmeal * 1 c Sugar, brown * 1/3 c butter; room temperature * 1/2 c hazelnuts; coarsely chopped (2 ounces) * whipped cream or vanilla ice cream