3 tablespoons vegetable oil
1½ pounds white mushrooms, trimmed and sliced thin
Salt and pepper
2 onions, halved and sliced thin
1 tablespoon minced fresh thyme or 1 teaspoon dried
1½ teaspoons sweet paprika
¼ cup all-purpose flour
¾ cup low-sodium chicken broth
¼ dried sherry
6 (6- to 8-ounce) beef blade steaks, ¾ to 1 inch thick
¼ cup heavy cream
2 tablespoons minced fresh parsley
1. Heat 1 tablespoon oil in 12-inch skillet over medium-high heat until shimmering. Add mushrooms and ¼ teaspoon salt, cover, and cook until softened, about 5 minutes. Uncover and continue to cook until mushrooms are dry and browned, 5 to 10 minutes longer; transfer to slow cooker.
2. Heat remaining 2 tablespoons oil in skillet over medium-high heat until shimmering. Add onions, thyme, and paprika and cook until onions are softened and lightly browned, 8 to 10 minutes. Stir in flour and cook for 1 minute. Slowly whisk in broth and sherry, scraping up any browned bits and smoothing out any lumps; transfer to slow cooker.
3. Season steaks with salt and pepper and nestle into slow cooker. Cover and cook until beef is tender, 9 to 11 hours on low or 5 to 7 hours on high.
4. Transfer steaks to serving platter and tent loosely with aluminum foil. Let braising liquid settle for 5 minutes, then remove fat from surface using large spoon. Stir in cream and parsley and season with salt and pepper to taste. Spoon 1 cup sauce over steaks and serve with remaining sauce.