Step 1: Brown the Beef and Onion - Heat the olive oil in a large, deep sided skillet over medium high heat. Once the oil is warm, add the ground beef, diced onion, salt, and black pepper. Let the beef sit against the hot skillet for a little while before you break it completely apart. That contact with the pan helps create those browned bits that add so much savory flavor. Continue cooking for about 5 to 7 minutes, stirring and breaking the beef into bite sized crumbles as you go. The beef should be fully cooked and the onion should look soft and translucent. If you have quite a bit of grease in the pan, carefully drain the excess before moving on.
Step 2: Build the Savory Flavor Base - Add the red pepper flakes and tomato paste to the cooked beef. Stir everything together and let the tomato paste cook for about 1 to 2 minutes. You will notice it darken slightly and start smelling sweeter and richer. That little bit of cooking makes a difference, so give it the time rather than immediately pouring in the broth. Stir in the minced garlic and dried thyme and cook for about 30 seconds. Garlic can go from fragrant to burnt pretty quickly, so once your kitchen smells garlicky and savory, you are ready for the next step.
Step 3: Simmer the Gnocchi and Vegetables - Stir in the Dijon mustard and Worcestershire sauce, making sure they are distributed throughout the beef. Pour in the beef broth and use your spoon to scrape along the bottom of the skillet. Those browned pieces stuck to the pan are full of flavor, and you want them in the sauce. Add the shelf stable gnocchi and frozen peas and carrots, then stir until everything is nicely combined. Cover the skillet and let it simmer for about 4 to 6 minutes, stirring once or twice so the gnocchi cooks evenly. When it is ready, the gnocchi should be tender when you bite into it. If the skillet starts looking too dry before the gnocchi is finished, stir in a small splash of additional broth or water.
Step 4: Make the Sauce Creamy - Reduce the heat to low before adding the heavy cream. Stir it gently through the skillet and let everything cook for another 1 to 2 minutes. You are not looking for a hard boil here. You just want the cream to warm through and blend with the beef broth, tomato paste, and all those savory pan juices. The sauce should begin looking smooth and creamy while still being loose enough to coat every piece of gnocchi. This is usually the moment somebody in my house walks through the kitchen and asks when dinner will be ready.
Step 5: Finish With Parmesan and Serve - Remove the skillet from the heat and sprinkle in the grated Parmesan. Stir until the cheese melts into the warm sauce and everything looks glossy and creamy. Give the sauce a taste and add a little more salt or black pepper if it needs it. Spoon the One Pan Gnocchi Shepard’s Pie into bowls while it is warm, making sure everybody gets plenty of beef, vegetables, and gnocchi. An extra shower of Parmesan and a small sprinkle of dried thyme on top makes it look especially inviting without adding any real work.