In a large bowl, beat butter and sugar with an electric mixer or spoon until creamy. Add egg white and vanilla; beat until blended. Stir in flour, oats, and cardamom. If making ahead, wrap crust mixture air tight and refrigerate up to 1 day. Crumble crust mixture over apple filling. Bake, uncovered, in a 350° oven until topping is richly browned. about 1 hour. Spoon dessert, hot or cool, into bowls and top with ice cream Makes 8 servings. Per serving 466 cal. (17 percent from fat); 3. 7 g protein 8.6 g fat (4. 7 g so t.); 98 g carbo.; 81 mg sodium; 19 mg chol. Apple filling. Core, peel, and slice 10 large (about 5 lb. total) tart apples (such as Gravenstein or Granny Smith) into a shallow 3 to 3-1/2,-quart casserole. Mix slices with 3/4 cup sugar, 1 tablespoon cornstarch, 1-1/2 teaspoons ground cinnamon and ?½ teaspoon ground allspice; use within 10 to 15 minutes.