Preheat oven to 325°F. Place ramekins in a baking dish.
Heat 1/3 cup sugar in a small pan over medium until it melts and turns amber. Pour caramel into ramekins and tilt to coat bottoms.
Whisk eggs, milks, 1/4 cup sugar, vanilla, and salt until smooth.
Strain mixture into ramekins over the caramel.
Fill baking dish with hot water halfway up ramekin sides.
Bake 30–35 minutes until set but slightly jiggly in the center.
Cool, then refrigerate at least 2 hours. Run a knife around edges and invert onto plates.