Hi Jess, you don’t disclose the answers you received from the Anova Support people and it appears you should rightfully feel unsure.
Is 57ᴼC both your cooking temperature and your target temperature? That’s about the midpoint between Medium-Rare and Medium doneness. By most standards Medium is 60ᴼC.
I don’t own an Anova oven, but most conventional ovens cannot cook at a lower temperature than about 75ᴼC, and that’s for a very good reason. It isn’t safe.
Precisely speaking, if your oven’s cooking temperature is set at 57ᴼC the meat’s internal temperature will never get to 57ᴼC. Over a sufficiently long period of time the internal temperature will approach that temperature, but never quite gets there. Meanwhile your cooking becomes a food safety matter as the meat’s internal temperature remains in the Food Danger Zone far too long allowing the growth of harmful pathogens. You don’t want that as hospitals are busy enough these days.
Jess, please don’t put a question mark at the end of a simple declarative sentence as i can’t know if you are asking a question or making a statement. If it is a question, i suggest you redirect your reading elsewhere as the information you have is not helpful.
You know when to stop cooking when the meat’s internal temperature attains your target temperature. That’s the purpose of using the probe thermometer. You know that.
If if this cook was doing 2 small pieces of lamb like yours equalling about half a whole boned leg of lamb the oven temperature would be preheated to 135ᴼC. First i’d whack up some onion, rosemary, lemon zest, garlic, a small pinch of red pepper flakes, and a few anchovy fillets. Simmer the mixture in olive oil til the onion is tender and allow the mixture to cool a bit. Season it with salt and pepper.
If you have the time and inclination, untie the meat or remove it from its netting and rub half the seasoning mixture over the inside of the meat. Then retie the roasts and slather the remaining mixture on the meat.
Place the meat on a wire rack set into a rimmed sheet pan. Insert the temperature probe and set the probe’s temperature’s alarm to 54ᴼC so you will end up with your target of 57ᴼC with carry-over residual heat.
Pop the meat in your oven and roast til done as you enjoy the delicious aromas wafting around your home. Remove the meat from the oven when the temperature probe’s setting has been attained. It should take about 2 1/2 hours, a little less if you use a 50% steam setting.
Normally, close to service time, i would pop a roast into a 260ᴼC oven for 10 to 12 minutes to crisp and brown the surface. However, your roasts are a little too small to do that without overcooking them.
And don’t forget to remove the twine before slicing.
Stay safe and enjoy.