Sift flour into a small pan. Toast the flour on low for 10 minutes stirring constantly so the flour doesn’t burn. Set aside and let the flour cool.
Peel, wash and slice mushrooms (you don’t have peel mushrooms; it’s just my preference to get rid of the top layer for cleaner cooking). Put mushrooms into a medium pan add 1 tbsp. of olive oil and sauté it on high. As soon the water evaporates, turn it off and remove from the hot stove top.
Peel, grate carrots and onion. Add grated carrots, onion, pressed garlic and all the spices to mushrooms and sauté for 5 minutes. Make sure you crush mushroom bouillon cubes before sautéing (it will be more difficult to crush when it heats. Chicken bouillon cubes crush easier when it heats, on the other hand).
Transfer the carrots and mushrooms to a medium sauce pan, and add 8 cups of water. Mix it and set aside.
Transfer cooled flour into a small bowl. Add water by a tablespoon at a time, mixing it every time you add water (if you add all the water at once, the flour mixture will get lumpy, so add water and mix little by little). The mixture will turn out very smooth and thick.
Add ketchup and heavy whipping to the smooth flour mixture and mix it well until all combined.
Add flour mixture to the gravy.
Mix it well. Place it on the stove and bring to a boil while stirring constantly (If you don’t stir constantly the flour will settle to the bottom and will burn). Remove from the stove, cover with cap. The gravy stays warm for a couple of hours before serving. Cover the gravy with a thick towel if you need it to stay warm longer. The gravy thickens as it gets cooler. Store left overs in the fridge. Reheat gravy on the stove by adding water to desired thickness.