Prep time: 30 minutes, plus cooling time
Cook time: 2 hours 45 minutes
This is not La Esperanza's recipe, but it is an authentic flan adapted from Diana Kennedy's "The Essential Cuisines of Mexico."
1/2 cup sugar
1 quart whole milk
1/2 cup sugar
1 vanilla bean
Pinch of salt
4 whole eggs
6 egg yolks
For the caramel: Melt the 1/2 cup sugar in a heavy pan over low heat. When it has completely melted, turn the heat up and stir the syrup with a wooden spoon until it darkens (the color will depend on how dark you like your caramel).
Pour the caramel into a flan mold, or a 1-quart charlotte mold or similar-size baking dish, and turn it around quickly, tipping the mold from side to side until there is an even coating of caramel over the bottom and halfway up the sides. Set dish aside.
For the custard: Preheat the oven to 350 degrees. Heat the milk in a heavy saucepan, add the sugar, vanilla bean and the salt, and let it simmer for about 15 minutes. The milk should be reduced by about 1/2 cup. Set it aside to cool.
Beat the eggs and egg yolks together well. Pour them through a strainer into the cooled milk and stir well. Pour the mixture through the strainer into the coated mold or dish. (Rinse the vanilla bean, let it dry, and store it for use again.)
Cover the mold and set it in a water bath on the lowest shelf in the oven. Cook the flan for 2 hours and test to see if it is firmly set. When it is done, set aside to cool.
(Flan can be refrigerated if made ahead: After it has cooled to room temperature, cover pan with plastic wrap and refrigerate. Return to room temperature for serving.)
To serve, gently run a knife along the inside edge of the mold or dish. Unmold by placing a large rimmed plate over the top of the mold, and carefully inverting it. Gently remove the dish.