I get Edwards & Sons Not Beef Boulion for my brown gravy.
The typical recipe is 1tbsp fat (butter, or vegan butter, or oil) 1tbsp flour, cook those together. The darker the flour the more flavor, but less thickening. Then add 1c of hot water mixed with 1 cube of the not beef. Slowly stir the water into the roux (fat flour mixture). You can thicken with your starch (mixed into a water starch slurry) of preference if needed.