Whichever kind of tomato you use will be fine — just don’t forget the chorizo de Bilbao. This legacy from the Spanish colonial era derives a lot of its aroma, color and flavor from the chorizo de Bilbao. And that makes it a lot different from other tomato-based stews. Chorizo de Bilbao is a spicy sausage packed in paprika flavored lard. In the Philippines, they are available canned, vacuum-packed or frozen. A bit expensive, but the flavor it gives a dish is just wonderful. Highly spiced, one chorizo de Bilbao is enough for this recipe.
Then, of course, the stock that comes from simmering the ox leg is incomparable. It is naturally thick and sticky. If available, choose bone-in ox leg. The flavor will even be richer.
Still not ditching the ox leg despite the comments in the old recipe that callos is Spanish for beef tripe? Nope. It is correct that callos is Spanish for beef tripe but callos in the Philippines is the stew and tripe is only one ingredient. Enough said. »