You won't need a braising pan when cooking beef topside, because it's a roast you can actually dry-roast instead of braise, as long as you baste it during cooking. Beef topside doesn't have an exact equivalent in American markets, but it's the most commonly used joint -- a British term for a beef cut made for roasting -- in the U.K. for pot roast. Taken from the uppermost portion of the hindquarter behind the sirloin, beef topside doesn't have much fat or connective tissue, so it's most tender when cooked to medium-rare or medium.
Take the topside out of the refrigerator about 45 minutes to 1 hour before you want to put it in the oven. If the topside isn't already tied, tie it with kitchen twine crosswise at 1-inch intervals, snugly enough to compress it evenly.
Salt the topside heavily with kosher salt and let it sit at room temperature in a dish. Place a few paper towels under it to absorb the moisture.
Heat the oven to 450 degrees Fahrenheit, which takes about 30 minutes. When the oven reached 450 F, scrape the salt off the topside and transfer it to a roasting pan.
Season the topside with freshly cracked black pepper, if desired, and slather it with oil.
Add 2 or 3 cups of stock, wine or another aromatic liquid to the pan, to use as a basting liquid. Topside doesn't have mush connective tissue, so it doesn't need liquid to tenderize it, but basting it with stock helps with the dryness that occurs because of its leanness.
Slide the topside in the oven. Roast the topside at 450 F for 15 minutes, then lower the heat to 400 F.
Baste the topside with the pan juices after you lower the temperature. If you want to roast chopped vegetables with the topside, add them now.
Roast the topside for 30 more minutes, bringing the total roasting time to about 45 minutes for medium-rare doneness, or to an internal temperature of 120 F. Roast the topside until it reaches 130 F for medium, and 140 F for medium-well.
Take the pan out of the oven and place the topside on a plate to rest. Don't cut the twine from it yet.
Rest the topside for 30 minutes, then cut the twine from it. Determine which direction the grain of muscle fibers go on the meat, then slice the roast across into 1/4-inch-thick slices. Serve with Yorkshire pudding and horseradish sauce for a traditional English Sunday roast.