Make and bake cake according to package directions for two 9-inch cake rounds. Cool for 15 minutes. In the meantime, mix Jell-o and boiling water: stir until Jell-o is dissolved. Turn cakes out on plates and poke holes in the top of both cakes with a drinking straw about 3/4 of the way down. Drizzle Jell-o over the holes (about 10 Tbs. for each cake ). Chill for 1-2 hours. In medium saucepan , cook sliced strawberries and sugar, stirring frequently. Bring to a boil. Mix the cornstarch in cold water and add to strawberries, stirring constantly until sauce thickens. Cool, while cakes are in the refrigerator. Remove cakes from refrigerator, and spoon strawberry mixture on top of one of the cakes, (there might be some leftover). Place the other cake on top. In a small mixing bowl, mix whipped topping and confectioners' sugar until well blended. Frost top and sides of cake. Slice fresh strawberries and make a big heart on top of cake with them and place more fresh sliced strawberries around the base of the cake and the top rim. Sprinkle with red colored sugar and serve.