Preheat the oven to 350°F / 175°C. Melt ¾ cup of sugar in a skillet over medium heat, stirring until liquid and golden amber.
Immediately pour into a 7in / 18cm round metal pan. Using oven mitts, tilt to coat the bottom; let the caramel harden.
Gently whisk 4 large eggs, 397g of sweetened condensed milk, 1¼ cups of whole milk, and 1 tablespoon of vanilla extract until combined. Pour over the caramel and cover tightly with foil.
Place the pan in a larger baking dish. Add water halfway up the sides and bake for 75 minutes, until set with a slight wobble.
Remove from the water bath and uncover. Cool, then cover and refrigerate for at least 4 hours.
Loosen the edges with a knife. Place a rimmed plate over the pan and carefully invert to release the flan and caramel.
