Okay, so just to clarify: according to Julia, aspic is the jellied stock that contains various items such as eggs and meat and vegetables. It’s a kind of composed salad.
Gelée is the jellified stock that you make aspic with.
Here’s what Julia says (in Mastering the Art of French Cooking) about gelée, or “homemade jellied stock”:
Calf’s feet and veal knuckles contain enough natural gelatin to make a stock jell by itself; pork rind helps the process. They are added to simmer with any of the stocks on pages 107 to 100 and will provide about 3 quarts of jelly.
Use either 2 calf’s feet OR 1 pound cracked veal knuckles AND 1/4 pound fresh or salt pork rind.
What is pork rind? I don’t even know! Ah, it is the skin of a pig. Thank you, Wikipedia.
OK, she says you can also use commercial gelatin… which I think I will do to start. I don’t happen to have a good source right at the moment for veal knuckles and pig skin. However, I do happen to have a whole canister of powdered gelatin because I use it in Kate’s homemade baby formula (gelatin helps babies digest cow’s milk).
One envelope of powdered American gelatin (1/4 ounce) is the equivalent of 4 sheets of French gelatin.
How to Use Powdered Gelatin:
Sprinkle 1 envelope of powdered gelatin into 1/4 to 1/2 cup of cold stock and let it soften for 3 to 4 minutes. Then blend it into the rest of the stock (use 1 envelope per 2 cups of stock) and stir over moderate heat for several minutes until the gelatin has completely dissolved and the liquid is absolutely free of granules.
How to Use Sheet Gelatin:
If you are living in France (hello, Louisa!), you will usually buy gelatin in sheets. Soak the sheets in cold water for about 10 minutes, until they are soft. Drain them, then stir them in the stock over gentle heat until the gelatin has completely dissolved.
Julia says you can add wine flavoring (port, Madeira, or cognac). We won’t be doing that since we are making baby food.
She also says it is imperative that you test your jelly:
Always test out a jelly before using it; the few minutes you spend can save you from disaster. Pour 1/2 inch of jelly into a chilled saucer and refrigerate it for about 10 minutes until it has set. Then break it up with a fork and let it sit at room temperature for 10 minutes. For aspics its broken lumps should stand alone, but not be rubbery. If the jelly is too hard, add unjellied stock and test again. If the jelly is too soft, add more gelatin and test again.