If she likes her steaks as rare as possible you should look into buying here a sous vide setup. You can get the whole steak to whatever doneness you want and then just quickly sear the outside. It gives me consistently good results.

I’ve been finding that reverse searing does a pretty good job without the sound vide

sous vide. Means "under vacuum". https://en.wikipedia.org/wiki/Sous_vide

Edit: I read a bit more on this, and was mistaken. Here is my original explanation: Basically a vacuum pump to lower boiling temperature; this puts a ceiling on achievable temperature for water-rich foods.

Actually, nowadays it looks like it's just slow cooking vacuum-sealed food in a temperature-controlled water bath.

Even as someone who has a sous vide set up, and uses it a lot, I prefer the results of reverse searing for decent quality steaks.

I have a sous vide set up as well, and while I find that it works great for chicken and duck, I agree with you that sous vide does something weird to steak. It's something about the texture. I know Kenji has written a few articles about how meat changes over different sous vide cooking durations, but I also wonder if the length of time changes the way fat renders somehow. I don't think it's been well studied. Searching the internet reveals I'm not the only person who has noticed this, but some people do not notice it, so there's not really a consensus on what's going on.

Wouldn't "as rare as possible" mean getting the steak to room temperature and then just searing? I always assumed the sous vide was more useful for those who liked their steaks more cooked.

Pretty much. A bleu steak is around 30 degrees internal temperature and really doesn't gain much from sous vide. Sous vide really only comes it its own for internal temperatures above 41-42 deg c. The advantage (compared to just searing/grilling) is that you can hold the steak at that point for longer, giving the protein more time to denature.

> likes steak as rare as possible

For pan searing, a quick and accurate thermometer doesn't actually make this much easier. I also have a Thermapen, but pan searing to a certain level of doneness is still a bit of an art because the final interior temperature after resting can be quite a bit different than the pull temperature due to residual heat at the edges of the meat. Even trying to get a consistent interior temperature using the same pan temperature (using a Control Freak induction cooktop) is difficult because the shape, thickness, and moisture content of meat can vary significantly. There's a few new gadgets that attempt to resolve this (e.g., this predictive thermometer with 8 sensors https://combustion.inc), but honestly having a lot of cooking experience is probably the best way to get a feel for when to remove the meat from the pan under rapid cooking conditions.

Of course, sous vide and reverse sear are completely different and while you can indeed get a precise temperature, those methods have their own trade-offs (namely, it's difficult to get as thick of a crust).

She has her methods. Mostly grilling. I don't interfere. :-)

She loathes sous vide.

The nice thing about the Thermapen is that it reads so fast that it's easy to explore the temperature gradients in the food. It's a learning process, right? In my own cooking, I'm correlating the measurements with technique and results, and when I finally cook something well I can reliably repeat it.

(Full disclosure. I have the surface temperature version of the Thermapen and a 4-channel recording thermometer, and I've profiled the oven, the griddle, etc. :-) We now focus on improving other aspects of cooking, confident that temperature is handled.)

> it reads so fast that it's easy to explore the temperature gradients in the food.

I was amazed when I discovered this. If you have a thick steak on a pan, knowing what the temperature gradient looks like inside is very valuable, compared to just knowing the temperature in the middle. Just slide your thermapen out slowly, and you can get a good reading on the gradient.