How to Make It
Prepare the Vanilla-Cabernet Butter: Combine dry red wine, sweet red wine, vanilla bean, and shallot in a small saucepan over high. Bring mixture to a boil, and cook without stirring, until mixture is thickened and reduced to about 1/4 cup, 15 to 20 minutes. Remove from heat, and cool for 20 minutes. Remove vanilla bean, scraping any syrup from bean, and discarding pod. (The mixture will have a thick syrupy consistency upon cooling.)
While syrup cools, place softened butter, parsley, salt, and pepper in the bowl of a stand mixer fitted with a paddle attachment. Beat butter on medium speed until fluffy, about 2 minutes. Using a spatula, gently fold cooled syrup into butter, creating ribbons of syrup through butter, without mixing completely. Wrap Vanilla-Cabernet Butter in a piece of plastic wrap; shape into a log (7 to 8 inches long). Chill log until firm, about 20 minutes.
Prepare the Steak with Mushrooms and Asparagus: Heat a 10- to 12-inch cast-iron skillet over high. Sprinkle steaks on both sides with pepper and 2 teaspoons of the salt, pressing gently into steak to adhere.
Heat olive oil in preheated skillet; add steaks to hot oil, making sure they do not touch each other, and cook undisturbed for 3 minutes. Turn steaks, and cook on other side undisturbed, 3 to 4 minutes, adding butter to skillet, and spooning melted butter over steaks while they cook the last 2 minutes, until a thermometer inserted in thickest portion of the steaks reaches 122°F, for medium-rare. Transfer steaks to a plate, and drizzle with lemon juice; tent with aluminum foil to keep warm. Allow steaks to rest 10 minutes before slicing.
Without wiping skillet clean, add mushrooms to skillet over medium-high, and sprinkle with remaining 1/2 teaspoon salt; cook, stirring often, until mushrooms begin to brown, about 5 minutes. Add asparagus and shallots, and cook, stirring often, until mushrooms are deeply browned, and shallots and asparagus are crisp tender, about 5 minutes.
Slice steak against the grain. Divide mushroom mixture and steak slices among plates. Add a pat of Vanilla-Cabernet Butter to each, allowing butter to melt onto steak. Serve immediately.