Beef Stroganoff

Name: Beef Stroganoff
Cuisine: Eastern European
Ingredients: 4 Tbsp. extra-virgin olive oil, divided; 2 Tbsp. unsalted butter, divided; 8 oz. crimini mushrooms, halved, quartered if large (about 2 cups); Kosher salt; 1 lb. skirt steak, cut into 4" sections; Freshly ground black pepper; 2 shallots, finely chopped; 4 garlic cloves, finely chopped; 1 Tbsp. double-concentrated tomato paste; 2 Tbsp. all-purpose flour; ¼ cup dry white wine; 2 cups (or more) low-sodium beef broth; 1 tsp. (or more) fish sauce; ¼ cup sour cream; Buttered cooked egg noodles and sliced scallions (for serving)