Eye of Round Roast with Jus

Name: Eye of Round Roast with Jus
Ingredients: 2 tsp. black peppercorns; 2 tsp. fennel seeds; 1 2½–3-lb. eye of round roast, trimmed; Kosher salt; 2 Tbsp. vegetable oil, divided; 1 lb. chuck stew meat, cut into 1 cubes; 1 medium red onion, sliced; 6 oz. crimini or button mushrooms, sliced; 3 garlic cloves, smashed; 2 Tbsp. double-concentrated tomato paste; 1 Tbsp. plus 1½ tsp. Worcestershire sauce; 1 Tbsp. soy sauce; 1 tsp. (or more) sherry vinegar or red wine vinegar; Flaky sea salt; Freshly ground black pepper; A spice mill or mortar and pestle