Strawberry Custard Torte

1 package (18-1/4 ounces) yellow cake mix
1/3 cup sugar
1 tablespoon cornstarch
1/8 teaspoon salt
1 cup milk
2 egg yolks, lightly beaten
1 tablespoon butter or margarine
1 teaspoon vanilla extract
1 carton (8 ounces) frozen whipped topping, thawed
1 package (12 ounces) frozen sweetened sliced strawberries, thawed and drained
Sliced fresh strawberries and mint leaves, optional

Prepare and bake cake according to package directions, using two greased and floured 9-in. round baking pans. Cool for 10 minutes; remove from pans to wire racks to cool completely.

In a saucepan, combine the sugar, cornstarch and salt; gradually stir in milk until smooth. Bring to a boil over medium heat; cook and stir for 2 minutes or until thickened. Remove from the heat.

Stir a small amount of hot filling into egg yolks; return all to pan, stirring constantly. Bring to a gentle boil; cook and stir for 2 minutes. Remove from the heat. Stir in butter and vanilla. Cover and refrigerate until chilled.

Place half of the whipped topping in a bowl; add strawberries. Split each cake into two horizontal layers; place one layer on a serving plate. Spread with half of the strawberry mixture. Top with a second cake layer; spread with custard. Add third layer; spread with remaining strawberry mixture.

Top with remaining cake and whipped topping. Refrigerate overnight.