Apple-Rhubarb Crisp

FOR THE TOPPING:
In a bowl, mix together the flour, brown sugar, sugar, nuts, and cinnamon. Work in the butter until the mixture resembles dry oats. The mixture should just hold together and look crumbly.

FOR THE FILLING:
Heat the oven to 350 degrees F. Peel, core, and quarter the apples. Cut each quarter into four chunks; you should have about 5 cups. Trim the rhubarb and cut it into 1-inch-long pieces 1/2 inch wide; you should have about 5 cups of rhubarb. In a large bowl, toss the apples and rhubarb with the sugar, flour, and cinnamon until well coated. Transfer the apple and rhubarb mixture to a 2-quarts baking dish and sprinkle the crisp topping over the top. Bake until the topping is golden brown and the fruit is bubbling, 1 hour to 1 hour 15 min. Cool slightly before serving.