1Butter a 9"-diameter cake pan. Line bottom with a round of parchment paper; smooth out. Coat sides with sugar, tapping out excess. Gently whisk egg yolks, eggs, cornstarch, salt, and 3/4 cup sugar in a large saucepan until smooth, then whisk vigorously until lightened in color, 1–2 minutes. Whisking constantly, gradually stream in milk, followed by 1 cup cream; scrape sides of pan. Scrape in vanilla seeds; discard pod. Cook mixture over medium heat, whisking constantly, until it starts to thicken, then whisk vigorously until it holds marks of whisk, 6–10 minutes. Immediately remove custard from heat (do not let boil); let cool slightly.
2Using a rubber spatula, press custard through a fine-mesh sieve into prepared pan. Chill, uncovered, 20 minutes (it should be warm but not hot). Place a rack in middle of oven and preheat to 400°F.