1. Begin by heating olive oil in a large skillet over medium-high heat.
2. Season the beef tips with salt and pepper while the oil is heating.
3. Add the beef tips to the hot skillet and brown them on all sides to develop flavor, but this step is optional.
4. Transfer the browned beef tips to your slow cooker.
5. In the same skillet, melt the butter and sauté the diced onions until translucent, about 3-4 minutes.
6. Add minced garlic to the onions and cook for an additional 30 seconds until fragrant.
7. Sprinkle the flour over the onion and garlic mixture, stirring to coat evenly. Cook for 1-2 minutes to remove the flour’s raw taste.
8. Gradually pour in the beef broth while whisking, ensuring no lumps form in the mixture.
9. Add Worcestershire sauce, paprika, marjoram, parsley, Italian seasoning, and thyme to the skillet. Stir everything to combine.
10. Bring the mixture to a simmer and cook for 2-3 minutes to allow it to thicken slightly.
11. Carefully pour the gravy mixture over the beef tips in the slow cooker.
12. Add a bay leaf to the slow cooker at this stage.
13. If adding mushrooms, include them now.
14. Cover the slow cooker and set it to cook on low for 6-8 hours or high for 4-6 hours, allowing the beef to become tender.
15. About 30 minutes before serving, taste the gravy and adjust seasoning if needed.
16. If a thicker gravy is desired, mix 2 tablespoons of cornstarch with 1/4 cup cold water and stir into the slow cooker. Cook on high for another 15-20 minutes until the gravy thickens.
17. Cook the egg noodles separately, following the package instructions (typically 8-10 minutes in boiling water).
18. Drain the noodles when they are al dente.
19. Either mix the cooked noodles with the beef and gravy in the slow cooker or serve the beef tips and gravy over the noodles individually.