I rarely use beef stock, although I occasionally stumble across recipes that require it. During winter, I dedicate a large amount of freezer real estate to tubs of chicken stock; something I make often and use frequently. However homemade stock can take up a lot of room, and I just don't have the space to also store large quantities of the lesser-used beef stock. To overcome this problem, yet still have supplies of homemade beef stock on hand, I make my own beef stock cubes.
Homemade beef stock cubes have all the convenience of a commercial stock cube, without the additives. They also contain a lot more beef. Read the ingredient list on almost any commercial stock cube. Beef is often listed as 2 - 3% of the total ingredients. The remainder of a commercial cube contains salt, sugar(s), modified starches, oils, yeast extracts and flavour enhancers, many present in larger amounts than the beef extract after which the cube is named.
I'm not going to lie. Making your own beef stock cubes does require a significant time investment. However, as I use a slow cooker to make the stock, the actual hands-on time is minimal. Beef bones are thicker and denser than chicken bones, so it takes longer to draw vitamins, minerals and gelatin out of the bones and into the stock. The longer the bones are simmered, the better the stock will be. I simmer beef bones for up to two days in my largest slow cooker, topping up the liquid level with boiling water as required. After a few days of largely ignoring the slow cooker, I am rewarded with a deeply flavourful stock.
After trial and error (mainly error) I have discovered it is better to let the stock cool before reducing it. Cooling the stock allows the fat to solidify on top, and it becomes easy to scoop off. Reserve any fat removed from the stock for other uses. I like to keep it beside the stove for frying. If the fat is not removed before the stock is concentrated, it will become emulsified in the stock itself resulting in a greasy stock cube. Not that I would know anything about that.
Stock cubes will keep in the fridge for at least a month due to the reduced water content. As I don't use them that often, I prefer to store them in the freezer, where they will last at least twelve months. This process can also be used to make chicken stock cubes. And if you can't be bothered making stock cubes, and have valuable freezer space to spare, just make the beef stock. At least you will know exactly what is in your food.