Preheat oven to 350. Mix melted butter, pecans, flour and brown sugar in medium bowl with fork until thoroughly mixed. Will be crumbly.
Place crumb mixture onto 10x15x1" cookie sheet, carefully spreading without packing to cover pan. Bake 10-15 minutes, stirring periodically to brown crumbs and avoid burning.
Remove crumbs from oven when lightly browned and set on cooling rack to cool, stirring periodically so that crumbs do not compact.
Next, place egg whites, partially frozen berries and lemon juice in large mixing bowl, beating with electric mixture at high speed for 15 minutes, until filling is a pink 'cloud'.
Fold whipped topping into strawberry mixture, carefully folding to not 'flatten' cloud.
Spread 3/4 of crumb mixture into 9x13 pan. Fill with strawberry mixture. Sprinkle remaining crumbs over top. Cover and freeze at least 4 hours, preferably day before serving. Cook time is minimum freezing time.
Note: Can replace frozen strawberries with 2 Cups sliced fresh strawberries, macerated with 1 Cup sugar. I prefer to use frozen strawberries that are set on counter while crumbs are prepared and baked. I have also substituted Whipped Cream for frozen topping. Place in cold bowl 1 cup heavy cream, and while beating add 2 tablespoons confectioners sugar, 1/2 teaspoon cream of tartar and 1 teaspoon vanilla extract. Fold into strawberry cloud in step 5.
2nd Note: Can use two 10" deep dish pie plates instead of 9x13" pan. Makes a great dessert to take to church suppers or dessert for a meal taken to sick friend.