Preheat oven to 325 degrees F.
Sear beef: While the chopped beef is still on the cutting board, toss it with 1 teaspoon salt and ½ teaspoon pepper. Heat 1 tablespoon vegetable oil in a large Dutch oven over medium-high heat. Once very hot, add half of the beef. Sear each side until deeply golden, about 4 minutes total. Remove to a plate using a slotted spoon. Repeat with remaining beef, leaving the drippings in the pot; set aside.
Vegetables: Melt 2 tablespoons butter with 1 tablespoon olive oil in the drippings over medium-high heat. Add the onions, carrots and celery and sauté until onions are softened, about 8 minutes. Add garlic and red pepper flakes and sauté for 30 seconds.
Roux: Reduce heat to medium. Add the flour and cook for 1-2 minutes, until the raw flour smell is gone.
Add broth: Reduce heat to low and slowly stir in the water, while scraping up the browned bits on the bottom of the pan. Add the beef base, Worcestershire, soy sauce, Dijon, and all seasonings. Stir in the seared beef.
Bake: Bring the pot to a simmer, cover, and transfer to the oven. Bake at 325 degrees F for 90 minutes OR until the beef is melt-in-your-mouth tender. Start the pasta water/cook the pasta the last 20 minutes of baking.
Noodles: Cook the egg noodles in a separate pot with salted water, just until al dente (check for doneness a couple minutes earlier than the package recommends). Drain and drizzle lightly with olive oil if the beef isn’t done cooking yet to prevent the noodles from sticking together. (The noodles are cooked separately because it’s not a good idea to boil beef or it gets tough).
Add half and half: Once the beef is tender, transfer the pot to the stove. Whisk the half and half with the cornstarch and stir it into the soup along with the diced tomatoes. Bring to a gentle simmer until thickened, about 3 minutes, adding the peas the last minute of cooking.
Combine: Stir in the noodles and season with salt and pepper to taste. Garnish with fresh parsley if desired.
