- The quality of the foie gras (livers)
- The cooking of it (temperature & time).
There are several different techniques for cooking a terrine of foie gras (sous-vide, poaching, oven, and en croute de sel or in salt) and each has its own little quirks, or I should say, "ways of doing it". At Ecole Ferrandi we learned how to cook terrines using the sous-vide method (under vacuum pak), and it didn't even have to be in a terrine per se. It could be wrapped in plastic wrap like a sausage & put in a sous-vide sac & then cooked to 66°C in a bain marie. At a two-Michelin star restaurant where I worked last year, the foie gras lobes were poached in goose fat to a temperature of 40°C and then stored for a long time before serving. See how variable it can be?
So what about cooking a terrine of foie gras at home? Seeing as we don't have a sous-vide machine....how do I best cook a terrine in my regular, old oven?
Let me share with you my recent experience. First the easy part: I prepared my foies de canard (duck livers) by de-nerving them & marinating them overnight in white port wine, cognac & some "foie gras spices" (typically lots of salt, pepper, some sugar, and 4-spices). Then I put it in the terrine. Now comes the tricky part: actually cooking it! A very reliable reference book of mine said to preheat the oven to 150°C & to cook the terrine in a bain marie for 20 minutes. It sounds so easy, doesn't it?! Well, it's not as straight forward as that. I came across the following variables which I believe impacted my actual cooking time.
- Oven temperature. Differences in temp do exist and size matters! A reading of 150°C was actually 165°C inside the oven. This is easily corrected, but something to be aware of and to check. As for size, when I open the door of my small oven, the temperature drop is much more significant than when I open the door of a large commercial oven. So, when I'm messing around with my terrine & bain marie here at home, I've got to be quick! This is probably only something to consider if you keep opening & closing the oven, like I did, when my terrine wouldn't finish cooking!
- Bain marie. Make sure your water is hot before you put your terrine in the bain marie! Using water from the tap without heating it will extend the cooking time considerably. My reference book doesn't say anything about this, but from experience I knew the water needed to be hot. Even then, I don't think it was hot enough. Next time I'll make sure it is ~ 70°C.
- Type of terrine you're using. Ceramic, cast iron, or glass - the type of material used will impact how long you cook your terrine. A cast iron terrine will take longer to come up to temperature in the bain marie than say glass or ceramic ones. Mine is cast iron. And I had stored it in the fridge before cooking it. Imagine what it did to the water temperature of the bain marie, and therefore the cooking time. Trust me, it lengthens it!
In the end it took me a total of 45 minutes. I removed the terrine from the oven when the temperature at center measured 30°C. At this point, my terrine looked like the one pictured in my reference book (ie, a good layer of melted yellow duck fat on top of the terrine), and as the book said, it may look undercooked, but that's the way it's supposed to be. I only wish I had a picture of it at that point. Too bad!
I removed the terrine from the bain marie, and let it sit on the counter top where it did continue to cook a bit. So, that reminds me that there's actually one last factor: the rate at which you cool down your terrine. At school, we cooked it until the center temperature was 66°C, but we immediately stopped the cooking by cold shocking it into an ice bath. Here at home, I let it sit on the counter a few hours.
I put weights on top to compress it. After a while, I removed them, wrapped the terrine in plastic and then let it rest in the fridge 3 days. (Letting it rest 3 days is critical.) Only then would I know how well it was cooked , or not. And, I'm relieved to say that it turned out delicious! Honestly, I wasn't sure if 30°C would actually be a good end temperature or not. It's just that my terrine looked like the picture of the terrine in my book. Unfortunately, my book doesn't define a target end temperature. I later read a few other blogs and found one that says to remove it at 38°C... so I leave it up to you to decide when you want to pull yours out of the oven!
My conclusions: (1) You're bound to run into variables that will affect the cooking process of a terrine of foie gras in the oven, and its successfulness. But, that shouldn't throw you off, if you're aware of the variables, and if you're able to adjust yourself to them. Blindly following a recipe without taking into account variables can lead to disaster no matter what you're preparing. And when you're cooking something costing a small fortune, it's even more important to pay attention to what you're doing. An overcooked terrine is simply a waste of money. I've done that before. Let me just say that it makes me not nice to be around for a few hours! You end up with a lot of rendered duck fat since most of the foie is melted away. What's left is a minuscule terrine. Still edible, but minuscule. An undercooked terrine is equally bad - it will look unappetizing (too pink/red) & that's enough to make it a turn-off. Plus, it is probably not the safest, bacterially-speaking. (2) Make sure you have a good food thermometer so that you can measure the temperature at the heart of the terrine. For me this is key to making a good terrine of foie gras, especially for beginners. Because this way, no matter what variable is thrown your way, you'll have a way to reassure yourself that it's going to be OK. (3) Finally, think about how these variables can occur, and try to mitigate them in the first place....then you'll really be on the road to cooking like a pro! Because after all, these are the same principles used in a professional kitchen for cooking n'importe quoi (no matter what)!
So voilà! I share the lessons I learned recently about making a terrine of foie gras at home. Long-winded, but hopefully, helpful. This one's for you Robbin! And please let me know what you've experienced in doing this yourself.