There's just no way to describe the usefulness of a meat thermometer without sounding clinical, as in "use this essential kitchen tool properly, and you won't end up in the clinic under the influence of the salmonella and e. coli that can result from undercooked meat."
Best of all is the affordability of meat thermometers. Target sells some for as little as $9.99, and The Everyday Gourmet's start around $12. Be sure to get one with a large enough dial for you to read clearly—I like the ones that include the types of meats and the temps for rare, medium and well-done. Most of the probes are slender and won't poke a big hole as you insert it properly to take a reading—be sure to follow whatever directions included with your meat thermometer.
Roulade of Pork Tenderloin Stuffed with Roasted Bell Pepper and Flat Leaf Kale
2 to 2 and 1/2 pounds pork tenderloin
2 qts. water
1/2 C. plus 2 T. salt
1/4 C. plus 2 T. sugar
1 cinnamon stick
1 star anise
1 t. peppercorns
1 t. fennel seeds
2 medium roasted red bell peppers, peeled, seeded, sliced and spread out flat
1/3 of a bunch of flat leaf kale, blanched in boiling water and shocked in ice water (Before blanching, trim the stems by holding the leaves in your hand and pulling the stem out; what you want will stay in your hand.)
2 T. chopped garlic
Olive oil, enough to sear
Pepper
Trim the pork of all fat, all sinew (the silver skin) and the membrane (the film that covers it). Slice lengthwise along the side of the tenderloin, but not all the way through, to butterfly the tenderloin. Place between two sheets of plastic wrap; pound out gently to about 3/8" thick. In a large pot, combine the water, salt, sugar, cinnamon stick, star anise, peppercorns and fennel seeds. Bring to a boil and then turn off the heat. Let stand 20 minutes, then chill until it's a bit colder to the touch than room temperature.
At this point you will brine the pork by adding it to the liquid, letting it sit in the refrigerator for an hour at least, but no more than three hours. Remove the meat from the brine and lay it flat. Spread the garlic across the meat. Then layer the slices of bell pepper and the flat leaf kale onto the tenderloin. Starting at one end, roll the meat over itself, pulling gently to make it tight, keeping everything inside as you roll. Tie securely in four to five places with butcher's twine. Heat a sauté pan with olive oil on high heat, and sear the loin on all sides until well-caramelized, then transfer it to an ovenproof dish and bake in a pre-heated 350-degree oven for approximately 30 minutes, until the internal temperature is 145 degrees Fahrenheit. Stick your meat thermometer into the rolled up tenderloin and read its dial—145 degrees and you're there. This temperature allows for the carry-over cooking that always takes place once a dish is removed from the heat. Let it rest for 5-8 minutes to keep the juices from running out when it's sliced. This is really good with mashed potatoes and grilled asapargus accompanied by pork jus drizzled around the entrée.
Pork Jus
1 to 1/2 C. tenderloin trimmings (no fat)
1/3 C. rough chopped onion
1/4 C. rough chopped celery
1/4 C. rough chopped carrot
1 sprig thyme
Half a bay leaf
1 t. peppercorns
5 parsley stems
1/4 C. red wine
2 1/2 C. chicken stock or vegetable stock (Chicken stock will taste better.)
Salt and pepper to taste
Olive oil to sauté tenderloin trimmings
Optional 2 T. butter, unsalted
Heat olive oil over high heat in a sauté pan or a rondo, a bigger saucepan with higher sides. Sear the trimmings until caramelized on all sides, then pull them out of the pan and reserve. Add onion, celery and carrot. Caramelize to a nice brown and pull out and reserve. You should see bits stuck in the bottom of the pan—fond. Deglaze the pan with red wine by swirling the pan and scraping with a wooden spoon to loosen the fond. All of this is flavor: Keep it. Reduce the red wine to about one tablespoon. Watch it carefully; you don't want to burn the sugar in the wine, or it'll turn bitter. Reduce the heat if necessary. Add the reserved trimmings and vegetables to the pan along with the herbs, spices and the stock. Bring to a boil and reduce to a slow simmer. The liquid should sort of smile, not bubble—just a bit of movement. Let that go for one to one and a half hours. Do not cover; do not stir. After the time has passed, strain and taste, but do not season yet. If you do, it will get saltier as it's reduced. You should have 1-1/2 cups of liquid. Take this and reduce it in a small saucepan over low heat, skimming off the fat and any solids that come to the top. Reduce it to about 3/4 of a cup. At that point, season to taste with salt and pepper. The optional butter could be put into the liquid now—chip it in a little bit at a time, over medium heat, swirling the pan until the butter is emulsified into the jus. Do not get it too hot, or it will separate. You want to end up with a glossy liquid, with or without the butter.