Mix oats, flour, brown sugar, cinnamon, salt and nutmeg in a small bowl. Cut in butter with a pastry cutter or two knives until the mixture resembles coarse meal. Stir in walnuts, if using. Cover and refrigerate (this mixture may be prepared 1 day ahead).
PREPARE FILLING:
Combine apples, cranberries, sugar and lemon juice in a large bowl; toss gently. Transfer fruit to prepared dish. Sprinkle refrigerated topping over fruit.
Cover with foil and bake 20 minutes. Uncover and continue baking until apples are tender and topping browns, about 40 minutes. Cool slightly.
PREPARE MAPLE WHIPPED CREAM:
In a large bowl, whip cream to soft peaks. Beat in 1 Tablespoon of syrup. Taste, adding more syrup if sweeter flavor is desired. Continue whipping to firm peaks.
Spoon warm crisp into bowls. Top each with a dollop of maple whipped cream and serve.
Notes
Note: The optional nuts in the recipe are not included in the nutritional information.