To make filling: Melt butter in heavy large skillet over medium high heat. Add onion, garlic and zucchini and sauté for 4 minutes until onion is soft.
Add kale and sauté for 1 minute. Add 1/3 cup vegetable broth, cover and cook for 6 minutes until kale is wilted.
Uncover and simmer for 2 minutes, until almost all of liquid evaporates.
Turn off heat and cool slightly. Season to taste with salt and pepper. Stir in cheese until melted.
In a medium bowl mix masa harina, baking powder, salt and pepper.
Using and electric mixer, beat butter and shortening until creamy.
Alternate adding the masa harina mixture and the vegetable broth in 3 additions, beating for about 6 minutes until fluffy. The dough should be soft and moist but shouldn’t stick when rolled into a ball.
Pat cornhusks dry. Place flat on work surface and spread with about 2 to 3 tablespoons of masa on the corn husk, then place some of filling atop masa.
Fold bigger sides in then pointy tip up over tamale. Repeat with remaining cornhusks, filling and masa.
To steam, place a coin (if it stops rattling it means your out of water and need to add more) in steamer with water. Line bottom of steamer with additional husks and stack tamales in steamer.
Top with additional husks and cover with a moist towel. Bring water to boil and cook for about an hour or until masa doesn’t stick to husks. Serve.