Place a fine-mesh sieve over a medium heatproof bowl. In a medium saucepan, whisk together 1/3 cup sugar, cornstarch, salt, milk, 1/2 cup cream, and egg yolks. Cook over medium-high, whisking constantly, until thickened and bubbling, 6 minutes. Reduce heat to medium-low and cook, whisking, 1 minute. Pour through sieve into bowl. Stir in butter and vanilla until combined. Press plastic wrap against surface of pudding to prevent a skin from forming and refrigerate 3 hours (or up to 3 days).
Toss strawberries with 1/2 cup sugar; let sit until fruit has released some juice, 20 minutes. Using an electric mixer, beat 1 1/2 cups cream and 1/4 cup sugar on medium-high until stiff peaks form, about 2 minutes.
In a large bowl or trifle dish, layer 1/2 the waffles, strawberries, pudding, and whipped cream; repeat. Cover trifle with plastic wrap and refrigerate at least 2 hours (or up to 1 day).
Any type of frozen waffle will work in the trifle; we like Belgian ones for their large nooks and crisp texture.