Homemade bouillon or portable soup is a simple, traditional way to keep stock always on hand without having to make it fresh every time. While the bouillon can be made without purchased gelatin, gelatin ensures that the bouillon comes together easily and firms up properly for long-term storage. Do not use vegetable scraps to flavor your stock as they may decrease the length of time you can store the bouillon and they will take much-needed space in your stock pot for gelatin-producing bones. You can purchase good quality bovine gelatin online (see sources).
Place the bones in a large baking dish, and roast them for 45 minutes.
Place the roasted bones, peppercorns and bay leaves in a large heavy-bottomed stock pot. Cover with filtered water and bring to a boil over moderately high heat, reduce the heat to medium low and simmer, uncovered, for eight to ten hours.
Strain the stock into a large mixing bowl through a fine-mesh sieve. Refrigerate for at least eight and up to twenty-four hours. You should have about one gallon of stock.
The stock should gel in the refrigerator, but it's not necessary. The fat will rise to the top of the stock. Pick it off and reserve it for another use such as frying vegetables or braising meat.
Transfer the stock to a shallow, wide-mouthed pot, stir in salt and bring to a boil over high heat. Continue simmering until the stock is reduced to 1 cup, about forty-five minutes depending on the surface area of your pot. Please note that the amount of time it takes to reduce 1 gallon of stock to 1 cup will depend on the size of your pan. A very wide and shallow pan will allow the stock to reduce in about 45 minutes, a traditional stock pot will take several hours.
Whisk gelatin into the hot stock and pour into a small container about 4 inches by 4 inches. Refrigerate for at least eight hours, cut into cubes about 1-inch by 1-inch. You can further dry out the cubes by setting them gently on a cotton cloth or napkin in the refrigerator or other cold place in your kitchen for a further eight to twenty-four hours.
Each cube of bouillon will produce one cup of stock. Simply drop the homemade bouillon cube into one cup hot water, stir to dissolve and serve. The bouillon cubes can be stored in an airtight container at room temperature for at least six months.