Moderately slow, you might even want to poach your corned beef.
Later in the week I'll blog about the concept of simmering: temperature, how it's different from poaching and boiling and why a cook would want to simmer - what's the point of having a nitro burning stove top if you aren't going to turn it up?
One of the very first good posts I did on this blog was about corned beef - you can read it here. Recap for those unwilling, unable or uninterested in linking...Corned refers to salting meat with grains (corn is a generic term for grain) of salt. Historically, corning could be done to any meat - lamb, ham or non-brisket, and in the UK corned beef means any meat from a can, while in the US corned beef means beef brisket.
In modernity, most corned beef is not going to be studded with large pellets of salt. I wouldn't call brining the current fad, but in lieu of air drying, aging or canning, brining is the go to method these days for imparting flavor and moisture (this is related to how livestock is raised in the new millennium, younger heads spend less time in the field, if at all). In Michael Ruhlman's Charcuterie, the author recommends 5 days of brining to 3 hours of cooking. Ruhlman is a smart dude, thoughtful cook and a good writer - there is no reason to doubt him or suggest this style of cooking is so anachronistic we might as well brine in wooden barrels.
But there are basically there are 3 different temperature ranges to braise tough meat like a brisket:
- 135-150ºf if you are going to cook for 12-48 hours.
- 160-170ºf for cooking times ranging 8-12 hours.
- 180-190ºf if you only have 3-4 hours to cook.
Who has time for 48 hours of low temperature cooking? Your crock pot/slow cooker does. It's hard to keep a stove top, even a back burner, even with lids at consistently low temperature. Ovens are worse, even if a heavy duty cast iron pot that will retain heat, the lowest setting is around 200, the heat comes on and off frequently. And even though I am nonplused by leaving the house with oven or a burner on low, this is not an activity I can talk into participating in. "Want to get a couple beers?", sure, they say. "Want to see a bad movie?", only if that smug Bradley Cooper isn't in it, they respond. "Place it on the smallest burner at the lowest setting and go to bed" and they tell me they don't want to die in their sleep.
I am making pot roast right now. I should have set it on the stove last night. Instead of doing 15 minutes work, I took some cough syrup, watched an episode of Parks and Rec and then slept for 10 hours. Yes, I was exhausted. So in order to have fork tender pot roast by 7 tonight, I'm poaching at around 160 for about 9 hours.
If your cooking medium never gets too much above the desired temperature (rare is 135 ish) it is impossible to overcook something. The tough muscle fiber, like the kind found in brisket, dissolves at 160º degrees, meat dries out at 140º. The longer you can afford to brine or keep the cooking temp below 120, the more the meat's connective tissues will break down. It is a balancing act. The best answer is always low and slow. The question is, how much time do you have.