Mix together brown sugar, pecans, flour, and melted butter, and spread in a 9 x 13-inch pan. Bake at 350° for 20 minutes. Stir 3 times while baking. Let cool. Take out 1/2 of mixture and set aside. Top: Combine egg whites, sugar, strawberries and lemon juice, and beat at high speed until peaks form. Fold in whipped cream. Spoon mixture into a 9 x 13-inch pan in which half of crumb mixture has been spread evenly on bottom. Sprinkle remaining crumb mixture on top. Freeze overnight.