Preheat broiler. Place whole poblano chiles on baking tray and cook, turning often, until well charred, about 10 minutes. Remove from oven and place in a bowl. Cover with a plate and steam for 8 minutes. When they are cool enough to handle, peel off charred skin, remove stem, seed and slice into strips. Reserve.
In medium frying pan, heat 1 tablespoon oil and add roasted poblano chile strips and onions. Cook over medium heat until they are nice and soft, around 8 minutes. Add corn kernels and 1/4 teaspoon salt. Let cool.
In medium bowl, combine crema and salsa. Mix well and reserve.
Prepare a deep rectangular pan by brushing with a bit of vegetable oil. Arrange 12 peeled tamales on bottom of pan. Top with 1/2 of the poblano mixture, followed by 1/2 of the crema/salsa mixture and 1/2 of the grated cheese. Repeat with another layer, finishing with grated cheese.
Place pan in a preheated 350°F oven and bake for 30 minutes or until cheese is nicely browned and edges look bubbly. Remove from oven and let stand for 10 minutes before cutting and slicing. Serve warm with salsa.