Maple Oatmeal Meringue Squares

1/2 cup (1 stick) unsalted butter
2 tablespoons pure maple syrup
1/4 cup lightly packed, very fresh light brown sugar
3 tablespoons granulated sugar
1/2 teaspoon maple flavoring
1 cup all-purpose flour, spooned in and leveled
2/3 cup quick-cooking rolled oats
1/4 teaspoon baking powder
1/2 teaspoon salt
1/2 teaspoon ground cinnamon

Meringue topping:
3 large egg whites, room temperature
1/4 teaspoon cream of tartar
1/4 teaspoon salt
3/4 cup lightly packed, very fresh light brown sugar
1 teaspoon imitation maple extract
1/2 teaspoon pure vanilla extract
1/2 teaspoon ground cinnamon
11/4 cups toasted walnuts, coarsely chopped, divided


1. Make crust: Position rack in center of  oven, and preheat oven to 350°F. Tear an 18" x 16" sheet of heavy-duty aluminum foil. Invert a 9" x 13" x 2" baking pan and center  foil over pan, pressing it across  bottom and down  sides. Remove foil, turn pan right side up, and place foil shell into pan, shaping it smoothly across  bottom and snugly against sides of pan. Using a pastry brush, grease bottom and sides of  aluminum foil with softened butter, taking care not to tear foil.

2. Place butter in a 3-quart saucepan and heat over a low flame until almost melted. Remove  pan from heat and stir in maple syrup. Set aside.  Place sugars and maple extract in bowl of a food processor fitted with steel blade. Pulse 2-3 times, then process for 5 seconds to thoroughly incorporate. Add remaining dry ingredients, pulse 5 times, then process for 8 - 10 seconds, or until mixture is consistency of fine meal. Empty into cooled butter/syrup and stir with a fork until a crumb mixture forms. Squeeze crumbs in your hands to form larger clumps of crumbs and scatter them evenly in bottom of prepared pan. Lay a strip of plastic wrap over top. Using a meat bâtarde or  bottom of a glass, press down to form a smooth, even crust. Remove plastic wrap.

3. Bake the crust for 16-18 minutes, or until set on top and beginning to brown.  Remove from oven, then reduce the oven temperature to 325ºF. When crust is almost done, prepare meringue topping.

4. Make meringue topping: Place egg whites in bowl of an electric mixer fitted with whip attachment. Whip whites on medium low speed until they are frothy. Add cream of tartar and salt, then increase mixer speed to medium high and whip to firm peaks. Add light brown sugar, two tablespoons at a time, taking about two minutes. Add extracts and cinnamon.  Beat about 15 seconds longer to form a shiny meringue. Using an oversize rubber spatula, fold in 1 cup of walnuts.   Spoon meringue over warm crust, spreading it evenly with back of a tablespoon. Sprinkle with remaining walnuts. Bake for 30 - 32 minutes or until it begins to pull away from sides of pan. Top will feel soft. Remove from oven and let cool on a wire rack.