Saute mushrooms in butter and olive oil. Set aside in a bowl.

Mince 1/4 of the onion. Saute in olive oil. Add garlic near end.

Add broth, vermouth and boil until reduced by about half. Season to taste with coarse kosher salt and pepper. Remove to the bowl with mushrooms.

Slide rest of onion into half-rounds. Saute over high heat just until starting to brown. Remove to the bowl.

Mix flour and mushroom powder in water to a paste.

Melt remaining 1 tablespoon butter in the skillet over medium-high heat. Working in batches, add beef pieces to skillet and sauté just warm, about 30 seconds per side. Transfer beef to plate; sprinkle with coarse salt and pepper. Add sliced shallots to same skillet, reduce heat to medium, and sauté until golden brown and tender, about 4 minutes. Stir in flour and tomato paste (mixture will clump). Add broth and paprika and whisk to blend, scraping up browned bits. Simmer until sauce thickens slightly, about 2 minutes. Season sauce to taste with coarse kosher salt and pepper. Remove from heat; cover and keep warm.

Add prime rib and any accumulated juices to shallot mixture in skillet; bring to simmer, stirring occasionally, then stir in sour cream. Remove from heat. Season to taste with coarse salt and pepper. Rewarm mushroom mixture over medium heat.

Stir in cream

Add bowl of beef mixture to mushrooms and stir to combine. Divide pasta into 4-6 bowls and spoon beef mixture over. Sprinkle with parsley and serve.