Spiralize the zucchini into pale green noodles. Toss with a pinch of salt in a colander, rest for 10 minutes, then thoroughly pat dry with paper towels.

Heat 1 tbsp (15g) butter in a large skillet over medium-high heat. Add sliced button mushrooms in a single layer. Let them sear undisturbed for 3 minutes until you achieve dark-edged sliced button mushrooms. Remove and set aside.

In the same skillet, add the ground beef and diced onion. Cook for 6-8 minutes, breaking it apart, until you have thoroughly browned ground beef crumbles. Drain excess fat if necessary.

Lower heat to medium. Add minced garlic and cook for 30 seconds. Pour in the beef broth to deglaze the pan. Stir in the Dijon mustard and simmer for 2 minutes.

Remove the skillet entirely from the heat. Gently fold in the sour cream and the reserved seared mushrooms. Stir until a thick, glossy, light beige sour cream sauce forms.

Briefly warm the dry zucchini noodles in a separate skillet for 1-2 minutes until tender. Plate the noodles in shallow bowls, generously ladle the dense and hearty stroganoff sauce over top, and finish with a delicate scattering of finely chopped bright green fresh parsley flakes.