Fill a medium saucepan with about 2 inches of water and bring to a boil; reduce to a simmer. In the heatproof bowl of an electric mixer, combine the eggs, yolk, 3 tablespoons sugar, and a pinch of salt. Set bowl over, but not touching, simmering water and whisk until egg mixture reaches 140 degrees on an instant-read thermometer. Transfer bowl to an electric mixer fitted with the whisk attachment, and whisk until mixture is thickened and forms ribbons.

Meanwhile, in the bowl of a food processor, combine 2 pints strawberries, remaining 1/2 cup sugar, lemon juice, and a pinch of salt. Pulse until finely chopped; set aside.

In the bowl of an electric mixer fitted with the whisk attachment, beat heavy cream until soft peaks form. Fold whipped cream into yolk mixture, along with 1/4 of the strawberry mixture, until well combined. Top the cake-filled molds with the yolk mixture, smoothing out the top so that it is even with the molds. Transfer to a freezer and freeze overnight. Refrigerate remaining strawberry mixture overnight.

Remove parfaits from freezer. Push strawberry parfaits from molds to remove, using a hot towel, if necessary. Let parfaits stand for 20 minutes.