1. Sprinkle pieces of meat with 1 tablespoon salt (1 1/2 tsp if using table salt), place on wire rack set in rimmed baking sheet, and let stand at room temperature 1 hour.

2. Adjust oven rack to lower-middle position and heat oven to 300°F. Heat 2 tablespoons butter in heavy-bottomed Dutch oven over medium heat. When foaming subsides, add onions and cook, stirring occasionally, until softened and beginning to brown, 8 to 10 minutes. Add carrot and celery, and continue to cook, stirring occasionally, for 5 minutes longer. Add garlic and cook until fragrant, about 30 seconds. Stir in 1 cup broth, 1/2 cup beer, porcinis, prunes, bay leaf, and thyme sprig; bring to simmer.

3. Pat beef dry with paper towels and season generously with pepper. Using three pieces of kitchen twine, tie each piece of meat into round loaf shape.

4. Nestle roasts on top of vegetables. Place large piece of foil over pot and cover tightly with lid; transfer pot to oven. Cook roasts until fully tender and sharp knife easily slips in and out of meat, 3 1/2 to 4 hours, turning roast halfway through cooking.

5. Transfer roasts to cutting board and tent loosely with foil. Strain liquid through mesh strainer into 4-cup liquid measuring cup. Discard thyme sprig and bay leaf. Transfer vegetables to pitcher of blender. Allow liquid to settle for 5 minutes then skim any fat off surface. Add beef broth as necessary to bring total amount of liquid to 3 cups. Place liquid in blender pitcher with vegetables and blend until smooth, about 2 minutes. Transfer sauce to medium saucepan and bring to simmer over medium heat.

6. While sauce is heating, heat remaining 2 tablespoons unsalted butter in 12-inch skillet over medium heat. When foaming subsides add crimini mushrooms and cook, stirring frequently, until all liquid has evaporated and mushrooms have started to brown, 7 to 10 minutes.

7. Remove twine from roast and slice against grain into 1/2-inch-thick slices. Transfer meat to large serving platter. Stir chopped thyme, remaining 1/4 cup beer, and sautéed criminis into sauce and season to taste with salt and pepper. Serve immediately, serving sauce separately.

Serves 6 to 8