Masa harina: This is cornmeal that has been prepared with lime or wood-ash lye water. It's different from ordinary cornmeal, cooks up softer, absorbs lots of fat during its cooking, holds together better in tortillas, etc. It's available from Mexican food stores.
To roast the fresh corn: just put them (in their husks) in a 400 degree oven for 5 minutes. Husks and silk will peel off easily. Then scrape off kernels, standing cob in a big frypan to catch them. Depending on the ears, it will take 2-4 ears to make 1 1/2 cups of kernels.
Cornhusk tamale wrappers: The ones you just prepared are probably dried out and frizzeled. If you've saved and dried husks, steep them in boiling water to cover (poured over them, not cooked) while roasting and scraping the corn. Otherwise, you'll have to use foil wrappers.
Simmer milk and corn for about 10 minutes. Strain the corn, reserve the milk, and puree 1/2 cup of the kernels with this milk, reserving the rest for putting in the tamale dough. Add the puree to the masa, mix vigorously with spoon and whisk. In a separate large bowl, whip the soft butter, baking powder, and salt together until very fluffy. Start adding the masa mixture about 1/4 cup (guesstimated) at a time whisking and beating vigorously after each dough addition. Spend 15 minuts at least beating the masa mix into the butter. Fold in the green chile, the remaining cup of corn kernels, and grated cheese.
Divide the dough into 8 equal pieces, about 4 Tbsp each. Pat each piece into a rectangle on a trimmed cornhusk to form a square or rectangle, leaving a husk border at the edges of the tamale at least 1 inch. Now fold up the rectangle along the length of the cornhusks and pinch it into a roll, loosely. Roll the husk up completely around the dough roll. Tie the ends with strips of cornhusk (traditional), or string (easier). The wrapping shouldn't be totally tight, so steam can get inches Place the wrapped tamales seam-side down on the rack of any kind of steamer (wok with a rack and tight cover will do, I use big enameled cast-iron frypan with tight lid). Tamales shouldn't touch the boiling water. Steam for 30 minutes. Let cool slightly and serve (diners unwrap their own) with any kind of hot tomato or other type of sauce. Those celebrating New Corn eat it without sauce, but fat or butter is sometimes available.