Set oven racks to lowest, and lower-middle positions. Preheat oven to 500°F.
Trim beef and cut into 1 1/2 to 2" chunks. Save scraps. Toss beef chunks with 1 1/2 tsp salt and let stand at room temperature for 30 minutes. Season lightly with pepper after 30 minutes.
Cut salt pork into 1/4" pieces. Toss with beef scraps. Place pork and beef scraps in large roasting pan with 2 tbsp butter. Place pan on lower-middle oven rack until well-browned and fat has rendered out, 15-20 minutes.
Meanwhile, trim mushrooms and cut in half if small, quarters if large. Toss mushrooms with pearl onions and sugar. Add 1 tbsp butter and pour onto rimmed baking sheet. Roast on lowest oven rack, stirring occasionally, until mushrooms wilt and release their moisture, moisture then evaporates, and vegetables are lightly glazed, 15-20 minutes. Transfer vegetables to large bowl, cover and refrigerate.
Remove roasting pan from oven. Reduce heat to 325°F Scrape meats to one side of pan. Sprinkle flour over fat in pan and whisk until no dry flour remains. Whisk in beef broth, 2 c red wine, gelatin, tomato paste and anchovy paste until combined. Add chopped onion, carrot, garlic, bay leaves, peppercorns, porcini mushrooms, parsley sprigs and thyme; stir to combine with meats. Arrange beef chunks on top of vegetables in a single layer. If liquid does not come 3/4 of the way up the beef chunks, add water until it does (do NOT submerge the beef completely). Return pan to oven and roast 3 to 3 1/2 hours, until meat is tender. Stir after 90 minutes. Add water as necessary to keep beef chunks half-covered.
Remove beef chunks and add to bowl with mushrooms and pearl onions. Strain liquid through a fine-mesh strainer into a large bowl, pressing the solids to remove as much liquid as possible. Discard solids. Add remaining wine and let stand 10 minutes. Using a wide spoon, skim as much fat as possible off surface and discard fat.
Pour liquid into Dutch oven and bring to a boil over medium-high heat. Simmer briskly, stirring occasionally, until liquid reduces and thickens to the consistency of heavy cream, 15-20 minutes. Turn heat down to medium-low and add beef, mushrooms and pearl onions. Cover and cook until just heated through, 5-8 minutes. Season with salt and pepper to taste. Stir in minced parsley and serve with buttered noodles or mashed potatoes. (Stew can be made up to 3 days in advance.).