1. Mix 1 3/4 cup dried masa harina (see left) with 2 cup plus 2 TBS hot tap water. Stir until it's doughy.
2. Beat a stick of softened unsalted butter with 1 teaspoon salt and 3/4 teaspoon baking powder until fluffy.
3. Add the masa to the butter and keep beating. Add 1/4 cup chicken broth, 2 small, grated zucchini, 1/2 cup finely chopped ham, 1/2 cup chopped watercress leaves, and 1/2 cup finely sliced green onion. Mix until well blended and put into an ungreased 9-inch pie plate. Place a buttered piece of parchment or foil on top of the tamal.
4. Set up a steamer that will accommodate the pie plate. (I use a wide soup pot with a trivet in the bottom.) Steam the tamal for 90 minutes, checking to be sure the water doesn't boil out. If it starts to get low, add more.
5. Let the tamal cool off and firm up for 15 minutes before serving. Serve with salsa and/or guacamole.