Remove husks and silks from corn, reserving 12 of the longest and widest pieces of husk. Immerse reserved husks in cool water.
Rinse ears. With a sharp knife, cut corn kernels off cobs. In a 1 1/2-to-2-quart pan, mix milk smoothly with cornstarch and cumin; add corn and chiles. Stir over high heat until boiling. Add cheese and stir until melted. Remove from heat and stir in egg yolks.
Drain husks and divide into pairs; make a cross of each pair. Nest a pair in each of 6 lightly oiled souffle baking dishes, 1 1/4-to-1 1/2-cup size. (If using frozen corn, omit husks and do not oil dishes.)
Put the 6 egg whites in a deep bowl; add cream of tartar and whip with a mixer on high speed until whites hold soft peaks. Stir about 1/3 of whites into corn mixture, then gently fold corn mixture into remaining whites; mixture can be streaked. Divide mixture equally among souffle dishes.
At once, bake in a 375 degree F oven until well browned; allow 20 minutes for creamy souffle centers, 25 minutes for firmer centers. Serve immediately with salt to taste.