1. If using masa harina, place it in a large bowl and reconstitute by adding 4 cups warm stock.
2. Beat with a wooden spoon or mix with your hands until you have a stiff, smooth dough like a medium-pliable bread dough.
3. Use a little more stock if necessary, but the mixture should not be loose.
4. Beat lard in the large bowl of an electric mixer on medium speed until very fluffy and fully aerated, about 3 minutes. It may take longer if your mixer is not very powerful. (A heavy-duty machine such as a KitchenAid.)
5. The best alternative to a mixer is not a spoon but your bare hand: whip and beat the lard with a rapid folding motion until you feel it lightening and continue to whip until it is fluffy and full of air. It should be as light as butter creamed for the lightest butter cake.