Prep + Sear Beef: Trim excess fat and connective tissues from 1.5-2 pounds ribeye steak and cut meat into approx. 1/2 inch cubes. Season generously with kosher salt and ground black pepper. Bring a large dutch oven to medium-high heat. Add 2 tablespoons of butter and let melt; swirl to coat the pan. Add beef and move around pan until pieces are seared and browned on the outside. No need to cook all the way through - they will finish cooking later. Remove from the hot skillet with a slotted spoon and set aside on a plate.
Cook Veggies: return the same large pot to medium high heat and add the 2 teaspoons garlic and onion. Move around until garlic is fragrant and onions have softened, about 2 minutes. Add 1 cup carrots, 1 cup celery, 1 cup baby bella mushrooms, and 1/2 cup russet potatoes. Move around pan while they cook - about 5-6 minutes.
Make Sauce: Add remaining 3 tablespoons of butter and let melt. Stir to coat the veggies. Add 1/3 cup all-purpose flour and stir to coat the veggies. Add 1/4 cup of the beef broth at a time and stir to combine. It will start as a thick paste and then it will thin out. Continue until all the broth has been added and repeat with 1/2 cup Guinness stout beer. Once fully combined, add 1 teaspoon Better Than Bouillon beef bouillon, 1/2 teaspoon soy sauce, 1 teaspoon worcestershire sauce, 1 tablespoon tomato paste, and 1 cup frozen peas to the pot. Along with the seared beef and any juices that have settled on the plate. Stir to combine.
Adjust + Simmer: adjust consistency, as needed. Add more beef broth, if it is too thick. If it is too thin, it will thicken as it simmers. Taste and add additional salt or pepper, as desired. Let simmer, uncovered 5-10 minutes to allow the veggies time to cook.
Storage: leftover stew can be stored in an airtight container for up to 5 days in the fridge or freeze in a freezer-safe container for up to 3 months.
Ribeye Substitution: don't want to splurge on ribeye steak - no problem - you can use chuck roast or really any other cut of beef. Just cut up into stew meat pieces.
Dairy Free: simply swap the butter for plant-based butter.