Frozen Strawberry Dessert

1 C all-purpose flour
1/4 C packed brown sugar
1/2 C butter, melted
1/2 C chopped walnuts
2 large egg whites
2/3 C sugar, divided
2 tsp water
1/8 tsp cream of tartar
1 pkg (10 oz) frozen sweetened sliced strawberries, thawed
2 T lemon juice
1 C heavy whipping cream

In a small bowl, combine the first four ingredients. Place in a 15 x 10 x 1-inch baking pan. Bake at 350 degrees for 18-20 minutes, stirring occasionally, until golden brown; cool on a wire rack. Set aside 1/3 cup for topping; sprinkle remaining nut mixture into a lightly greased 1 3x 9-inch dish.  In a large saucepan, combine the egg whites, one tablespoon sugar, water, and cream of tartar over low heat. With a portable mixer, beat on low speed for one minute. Continue beating on low speed until mixture reaches 160 degrees. Pour into a large bowl. Add strawberries, lemon juice, and remaining sugar; beat on high for eight minutes or until light and fluffy.  In another large bowl, beat cream until stiff peaks form.  Fold into strawberry mixture. Transfer to prepared dish; sprinkle with the reserved nut mixture. Cover and freeze for six hours or overnight.