Heat the olive oil in a large, heavy-bottomed skillet or Dutch oven over medium heat. Season the beef with salt and pepper (I start out with about 1/4 tsp of each). When the oil begins to shimmer, add the ground beef to the pot, breaking it up into tiny chunks as it browns. When all traces of pink are gone, remove as much of the rendered fat in the pot as you can, either by tilting the pot and spooning it off, or by draining the meat in a fine-mesh colander.
Add the onion to the skillet with the beef; sauté until translucent and soft, about 5 minutes. Add the garlic and mushrooms; continue to sauté until the mushrooms have given up their juices.
Stir in the mustard, herbs, broth, and pasta. Mix well. Bring to a simmer and cover the pot.
Cook until the pasta is done to your liking, stirring occasionally. This will take anywhere from 16-20 minutes, depending on whether you prefer your pasta al dente or soft.
Stir in the sour cream and check the pasta for seasoning, adjusting as necessary. Serve topped with a tiny pinch of your fresh herb of choice. Enjoy!