A weeknight one-pot: ground beef, cremini, and orzo in a thyme cream sauce. Built like a beef stroganoff, with Dijon standing in for the sour cream and orzo cooked right in the pan.
Heat the butter and olive oil in a wide, deep skillet over medium-high. Add the mushrooms in a single layer, leave them undisturbed for 2 minutes to brown, then stir, season with a pinch of salt, and cook 3 minutes more. Move them to a plate.
In the same pan, soften the onion over medium heat with a pinch of salt, about 4 minutes. Add the garlic and thyme and cook 1 minute until fragrant.
Add the ground beef, break it up, and brown through. Stir in the Worcestershire and Dijon (and the tomato paste, if using, cooking it 1 to 2 minutes until it darkens). If you're using white wine instead of lemon, add a splash now and let it cook off.
Pour in the beef stock, bring to a boil, then stir in the dry orzo and drop to a steady simmer. Cook 10 to 12 minutes, stirring frequently so the orzo doesn't catch; if the pan dries before the orzo is tender, add the reserved stock a splash at a time.
Lower the heat. Stir in the cream and the reserved mushrooms, and simmer 2 to 3 minutes until the sauce is glossy and coats the orzo. Stir in the lemon juice (skip if you used wine) to cut the richness. Taste, then season with salt and pepper, going easy on the salt given the stock, Worcestershire, and Parmesan already in the pan.
Finish with parsley and a generous grating of Parmesan. Optional: scatter Crispy Shallots for crunch against the soft, rich orzo.