Bring a large pot of water to a boil, add in potatoes and boil until potatoes are tender, about 8-10 minutes.
In a large pot, melt butter over medium-high heat. Add in carrots, cook for 1-2 minutes, then add in onion and celery. Season vegetables with 1 tablespoon of Montreal Steak seasoning. Cook until onions are translucent and the vegetables are just tender.
Add in water and chicken base, and bring it to a boil. Let it simmer over medium heat for 10-15 minutes.
Whisk flour and half-and-half or milk together vigourously. Pour into the pot and stir.
Add in frozen peas, potatoes, and cubed chicken, add remaining 2 tablespoons of Montreal steak seasoning and salt and pepper to taste.
Bring to a boil and then reduce heat to low and simmer. Cover with a lid, cracked slightly to vent, and simmer for 15-20 minutes or until thickened.
Remove from heat and let it sit for 5-10 minutes to cool, then serve and enjoy.