Step 1: Mix the Meatball Base - Add the ground beef, kosher salt, black pepper, garlic powder, dried parsley, cowboy butter seasoning, Italian breadcrumbs, Parmesan, and eggs to a large bowl. Use clean hands or a sturdy fork to bring everything together gently. Stop as soon as the ingredients look evenly distributed. I know it is tempting to keep mixing until the bowl looks perfectly uniform, but too much handling presses the meat together and can make the finished meatballs firm instead of tender.
Step 2: Roll the Meatballs - Scoop the mixture into about 20 to 24 portions, then roll each portion lightly between your palms. Try to keep them close to the same size so they finish cooking at the same time. A cookie scoop is handy here, but a spoon works just fine. Set the shaped meatballs on a plate as you go, and do not pack them too tightly. A light touch gives you a softer center.
Step 3: Brown and Cook the Meatballs - Place a large skillet over medium heat and add the meatballs in a single layer. If your skillet is crowded, cook them in two batches so they brown instead of steaming. Turn them every few minutes until the outside is nicely browned and the centers reach 160°F on an instant read thermometer. This usually takes about 12 to 16 minutes depending on their size. Transfer the cooked meatballs to a clean plate and keep them nearby.
Step 4: Prepare the Skillet - Look at the drippings left in the pan. If there is a large amount of grease, carefully spoon most of it out, leaving behind a thin layer of browned bits because those bits carry a lot of flavor. You can wipe the skillet clean for a milder sauce, but I usually leave the browned goodness in place. Add the unsalted butter and let it melt over medium low heat, scraping the bottom gently with a wooden spoon.
Step 5: Build the Cowboy Butter Sauce - Pour in the heavy cream, then whisk in the Worcestershire sauce, Dijon mustard, garlic powder, dried parsley, and cowboy butter seasoning. Keep the heat moderate and bring the mixture to a gentle simmer. You want small bubbles around the edge rather than a hard boil, since high heat can make a cream sauce separate. As you whisk, the browned bits from the skillet will melt into the sauce and give it a deeper, meatier color.
Step 6: Melt in the Parmesan - Sprinkle the freshly grated Parmesan into the simmering sauce and stir steadily for 2 to 3 minutes. The cheese should melt smoothly and the sauce should thicken enough to coat the back of a spoon. If it looks too thick, add a small splash of cream. If it still seems thin, let it simmer for another minute while you stir. Remember that the sauce will continue to thicken slightly as it cools.
Step 7: Coat and Finish the Meatballs - Return the cooked meatballs and any juices from the plate to the skillet. Gently turn them through the sauce until every meatball is coated, then let everything simmer together for 2 to 3 minutes. This last little rest in the skillet warms the meatballs through and lets the sauce settle into their browned edges. Finish with chopped fresh parsley and serve while the sauce is hot, creamy, and easy to spoon.