All cava producers start out as makers of still wine first. Short of buying in still wines made by another producer (a practice that I haven’t actually heard of and one that I’m not sure would be permitted anyway, though I do know of at least one producer who does the reverse ā makes the still wines and asks another to finish the fizz) how would they come by their base wines?
It’s the base wines that are the obvious prerequisite of all sparkling wines. The second fermentation, provoked by the addition of sugar and yeast, can only take place if there has already been a first fermentation! This is the making of the still wines that are to form the base for the sparklers to come.