This batter is key to bringing out the best flavor in your tamales.
In the bowl of an electric mixer fitted with the paddle attachment, combine the lard, baking powder, and salt. Beat until light and fluffy. Add 1 cup masa and 1/3 cup stock; beat until thoroughly combined. Add the remaining masa and 1/3 cup stock; beat until light and fluffy, about 2 minutes. The batter should be soft but hold its shape in a spoon. If using fresh masa, test the batter to determine if it is adequately fluffy, ensuring light and tender tamales: Drop 1 teaspoon batter into a cup of cold water. If it floats to the surface, it is ready. Refrigerate at least 1 hour. Store batter in an airtight container, refrigerated, up to 2 days.
When making this batter, choose stock that best suits the tamale recipe in which you'll use the batter. If you cannot find freshly rendered pork lard, use solid vegetable shortening instead, not canned or packaged lard.