Make-Ahead Cream Puffs

1 ? cups 2% milk, divided
? cup granulated sugar
3 tablespoons cornstarch
1/8 teaspoon salt
2 large eggs
1 teaspoon chilled butter, cut into small pieces
2 teaspoons vanilla extract
1 cup frozen fat-free whipped topping, thawed

1 cup water
2 tablespoons butter
2 teaspoons granulated sugar
? teaspoon salt
1 cup all-purpose flour
2 arge eggs
2 large egg whites
1 teaspoon powdered sugar

To prepare filling, heat 1 ? cups milk in a medium, heavy saucepan to 180, or until tiny bubbles form around the edge. Do not boil.
Combine remaining ? cup milk, ? cup granulated sugar, cornstarch, 1/8 teaspoon salt, and two eggs in a medium bowl, stirring well with a whisk.
Gradually add the hot milk to the sugar mixture, stirring constantly.
Place milk mixture in pan. Add one teaspoon butter and cook over medium heat until thick and bubbly, about three minutes, stirring constantly. Reduce heat to low and cook two minutes, stirring constantly.
Strain mixture through a sieve into a bowl. Stir in vanilla. Place plastic wrap directly on surface of filing and refrigerate two hours or until chilled.
Fold in whipped topping. Cover and chill.
Heat oven to 425.
To prepare shells, cover a large, heavy baking sheet with parchment paper.
Combine water, 3 tablespoons butter, 2 teaspoons granulated sugar, and ? teaspoon salt in a large saucepan over medium heat, stirring occasionally with a wooden spoon. Bring to boil and remove from heat.
Lightly spoon flour into a dry measuring cup and level with a knife. Add flour to water mixture, stirring well, until smooth and mixture pulls away from sides of pan.
Return pan to heat and cook 30 seconds, stirring occasionally.
Remove pan from heat. Add 2 two eggs and egg whites, one at a time, beating with a mixture at medium speed until just combined. Beat one minute at medium speed.
Drop dough into 10 mounds (about ? cup each) two inches aprt on baking sheet.
Bake at 425 for 20 minutes. Reduce heat to 350 (do not open door) and bake an additional 20 minutes.
Turn oven off and partially open over door. Pierce the top of each puff with a knofe and cool 20 minutes. Remove from oven and cool completely on a wire rack.
Cut off top third of puff and fill with one tablespoon of filling. Replace tops and sprinkle with powdered sugar.