The Basics

• You could refer to just about any set dessert made from cream and milk as panna cotta. Classic panna cottas of Italy, where the dish hails from, use gelatin as the thickening agent, while British versions, one of the first regions the dessert migrated to, use corn flour as the thickener. Progressive or modernist takes on panna cotta employ food additives such as agar-agar, an algae extract, as the gelling agent because of its stabilizing and emulsifying ability. You could use any gelling agent to set the cream and milk, but for the sake of simplicity, use the basic flavorless gelatin packets you get in the supermarket. They allow for a simple ratio of dairy to gelatin you can adapt to any size dish of panna cotta.

Ratio

• A well-executed panna cotta has a combination of semi-firmness to wobbliness on the plate, and smoothness to crispness on the palate that come from a balanced dairy-to-gelatin ratio. Other ingredients, such as sugar, vanilla, saffron or whatever else you add to it to make it your own, aren't what make a panna cotta a panna cotta -- it's how the cream tiptoes the line between barely set and firm. You can attribute this balance to a 72-to-1 ratio of dairy to gelatin, or 4 cups of heavy cream to 1 tablespoon of powdered gelatin.

Volume

• Before you can adapt the ratio to your dish, you need to know its volume. You can figure the volume the hard way, by multiplying its length, width and height together and converting the product to cups, but there's an easier way. Simply fill the dish with water then empty the water into a measuring cup, adding up how many cups it holds as you do. For example, if you can fill four 4-cup measuring cups with the water from the dish, the dish holds 16 cups, and you would make a 16-cup batch of panna cotta.

Technique

• Start by portioning the cream in a heavy-bottomed saucepan. If your dish has a 16-cup volume, pour 16 cups, or 1 gallon, of heavy cream in the saucepan along with the sugar. Start with 1 tablespoon of sugar for every cup of cream, then taste and add more if desired. Set the heat to medium and cook until the sugar dissolves, about 10 minutes, stirring occasionally but not scraping the bottom of the pan. In a separate bowl, sprinkle the gelatin over four times as much cold water and let it bloom. For example, if you need 4 tablespoons of gelatin, sprinkle it over 16 tablespoons of cold water. Let the gelatin stand for about five to 10 minutes, then pour the warm cream over it and stir until incorporated. Lightly oil the large dish and pour the panna cotta in it. Place the panna cotta in the refrigerator and wait two hours for it to set. Place the serving dish on top of the large dish, then invert both of them and lift the dish away to unmold.