Heat the stock until warm. Using a mixer with a paddle mix the masa and salt, add in the stock while mixing until the dough is like a soft playdough. Remove the dough from the mixer and using the wisk attachment mix the shortening until it is very fluffy. Switch to the paddle attachment and mix the dough into the shortening 2 cups at a time. Use in any tamales. This is an adaptation from Tamales 101.