To make the marinade: Place the ginger, garlic, salt, cumin, chili powder, turmeric, and pepper in a food process and finely chop, scraping down the sides of the bowl with a rubber spatula.  Add the lemon juice and 1 tablespoon vegetable oil and puree.  Add the sour cream and yogurt and pulse the processor in short bursts, just to mix.  Transfer the marinade to a nonreactive mixing bowl.

Wipe the mushrooms clean with damp paper towels.  Stir them into the marinade, covered, in the refrigerator for 30 minutes.

Preheat the Hōmdoor to 450-500 degrees F.

Thread the mushrooms on Hōmdoor skewers.  Place the skewered mushrooms in the Hōmdoor and cook until lightly browned on the outside, 2 to 3 minutes. Baste with oil and continue cooking until golden brown and tender, 1 to 2 minutes more.  Serve at once.