Preparation

• Combine flour, sugar, and salt in a large bowl. Cut the cold butter and shortening into small cubes and add to the flour mixture. Work the butter and shortening into the flour until the mixture resembles coarse breadcrumbs. Add cold water one tablespoon at a time, tossing with a fork until the dough just comes together. Form into a disk, wrap in plastic, and refrigerate for at least 30 minutes.
• While the dough chills, peel and slice the apples into wedges and slice the rhubarb. Combine the apple slices and rhubarb with brown sugar, flour, cinnamon, ground cloves, nutmeg, lemon juice, and vanilla extract. Toss gently until the fruit is evenly coated.
• Preheat oven to 375°F. Roll one half of the chilled dough into a circle about ⅛-inch thick and fit it into a 9-inch pie dish. Prick the bottom and sides with a fork.
• Bake the crust for 12-15 minutes until set but not golden. Roll out the remaining dough into thin strips for a lattice pattern.
• Remove the pre-baked crust from the oven and fill with the fruit mixture. Weave the dough strips over the filling and brush with egg wash, then sprinkle with sugar.
• Bake the pie at 375°F for 35-40 minutes until the top is deep golden brown and the filling bubbles slightly. Let cool for at least 2 hours before slicing.