Prepared pastry for a single-crust pie
1/3 cup walnut pieces
6 Granny Smith apples (about 2 1/4 pounds), peeled, cored and thickly sliced
1 tablespoon lemon juice
1 teaspoon cinnamon
5 tablespoons cold, unsalted butter, divided
1/2 cup honey
1 cup packed brown sugar, divided
2 cups 1-inch-sliced rhubarb
1/4 cup instant tapioca
1/2 teaspoon kosher or sea salt
1/2 cup flour
Line a pie plate with the pastry crust and place in refrigerator while you prepare filling. Preheat oven to 375 F. Spread the walnuts on a baking sheet and toast in oven for about 5 minutes, until there's a warm, nutty aroma. Cool, then chop coarsely and set aside.
Toss the apple slices with the lemon juice and cinnamon. Set aside.
Melt 1 tablespoon of the butter with the honey and 1/2 cup of the brown sugar in a large, heavy saucepan; heat, stirring continuously, until mixture comes to a rolling boil. Add apples, stirring to coat them with caramel. Reduce heat and cook, uncovered, for no more than 5 minutes. Do not overcook apples to mushiness.
Place the rhubarb in a bowl. Using a slotted spoon, transfer hot apples into bowl with rhubarb. Add the tapioca and stir to combine. Let sit for 15 minutes. Meanwhile, add the salt to caramel remaining in pan and cook, stirring often, for a few minutes more to reduce it to a thick syrup. Do not let it scorch. Remove from heat and set aside.
Cut remaining 4 tablespoons butter into small cubes and combine in a bowl with the flour and remaining 1/2 cup brown sugar; pinch butter with your fingers until evenly distributed. Stir in toasted walnuts.
Scrape apple-rhubarb mixture into chilled pie shell and drizzle with 3 tablespoons caramel. Spread streusel mixture over pie and bake in preheated oven for 30 minutes. Let cool on a wire rack for at least 30 minutes.
Just before serving, drizzle remaining caramel (reheating if necessary) over pie. Makes 6 to 8 servings.
— Recipe from "Rhubarb Renaissance," by Kim Ode (Minnesota Historical Society Press, 120 pages, $16.95).