The mustard sauce is perfect with the tenderloin as it keeps it really moist. Tenderloin being very lean would tend to get dry easily, so a short cooking time and a good sauce are required.
I start by chopping about half a pink onion and cleaning some nugget potatoes. I start a large cocotte Le Creuset with 3 tbsp olive oil on medium high and brown all together the onion, the potatoes, and the whole tenderloin with sage and thyme. After 5 minutes, I deglaze with 1/4 cup cider vinegar, 1/4 cup dry white wine and 1/2 cup H2O. I add 1/4 cup chopped parsley, salt and pepper and cover on low for 30 minutes. Mushrooms and other vegetables like golden beets can also be included then.
Everything should be cooked within the half hour, I remove it all from the cocotte, slice the meat and reserve it in a hot serving dish on the side, while I add 4 tbsp Dijon Mustard to the sauce, stir well and cook this for 5 minutes. If the remaining mixture is not enough, just add a bit of water, but I had just the right amount left. The mustard has to cook, as this will mellow its taste. The sauce will look like a cream sauce and will be a little tart but not like eating mustard. Pour the sauce over the meat. Rice and mashed potatoes also go well with this. No need for cream, but of course, if you want to indulge, add 1/2 cup 30% cream and stir on low for another 5 minutes. Below, tonight’s dinner without cream!