In a large saucepan, heat up a knob of butter (the more, the merrier!)
Add the carrots, celery, and onions to the pan.
Add the thyme, parsley, mushrooms, bay leaves, garlic, and the tomato paste.
Mix everything together. Over a medium-high heat, cook the veggies down until it's deeply caramelized, about 35-40minutes, with an occasional stir. If your pan dries out, add a touch more butter.
This is what the mixture will look like after it's been cooked down and caramelized. Yum.
Slowly add the water and allow everything to come to a simmer. I eventually added all 4 cups of water.
Let it simmer for 20-25 minutes until it's thickened and rich.
Strain the mixture with a fine strainer, pushing down on the veggies to extract all the flavor.
Salt to taste and there you have it - a delicious, savory gravy with rich and complex flavors that goes well on everything!