Bring a large pot of water to a boil.
Add the almond flour, paprika, 1 tsp salt and 1 tsp pepper to a large shallow bowl and toss to combine. Dredge the strips of meat in the flour mixture, shake them to remove excess flour, then put them aside.
Place a large skillet over high heat and swirl in 1 tbsp avocado oil. When the oil begins to shimmer, sauté the beef slices, until they are well browned on both sides but rare inside, about 3 to 4 minutes. Transfer the seared meat to a bowl. Turn the heat down slightly.
Add 1 tbsp of avocado oil to the pan. When it's hot, add the chopped onion and mushrooms, and season with salt and pepper. Cook, stirring frequently, until the mushrooms have released their moisture, 8-10 minutes.
While the mushrooms and onion cook, add the pasta to the boiling water, and cook until just done, about 5-6 minutes. Drain the pasta, and set aside.
When the mushrooms and onions are soft and caramelized, slowly stir in the coconut milk followed by the mustard. Add the meat, along with any accumulated juices, and stir to combine. Cook, stirring occasionally, until the beef is medium-rare, 2 to 3 minutes. Add the pasta and stir. Taste, and adjust the seasonings.
Serve. Sprinkle with parsley if desired.