GARAM MASALA: Grind the cardamom seeds, cinnamon, black cumin seeds, cloves, black peppercorns, and nutmeg. Makes about 3 tablespoons.
Warm the oil in the large pan over medium-high heat. Add the onions and stir for 3 minutes.
Add the sliced tatsoi, chile, ginger, salt, and sugar, stirring and cooking for 5 minutes.
Add the water and bring to a simmer. Cover tightly and and turn heat down to low, cooking for 10 more minutes. Remove the lid and boil away some of the extra liquid. Sprinkle garam masala over the top and stir.