Grease a 13-by-9-by-2-inch glass baking dish with butter. Set aside.
For the crepe batter: Place all ingredients in a blender and process until smooth. Let the batter stand for 30 minutes to allow any bubbles to settle.
Preheat oven to 350 degrees F.
For the sauce: Melt 2 tablespoons butter in heavy large skillet over medium-high heat. Add the onions and cook until translucent, about 4 minutes. Add the poblano chiles and cook for 1 minute to blend flavors. Add the heavy cream and bring to a boil. Reduce the heat to medium and simmer until reduced and the cream coats back of spoon, about 6 minutes. Cool mixture slightly then transfer to blender and process until smooth. Season the poblano sauce with salt and pepper, to taste. Return the sauce to the same skillet and keep warm over low heat until ready to serve.
Heat a 10-inch-diameter non-stick skillet over medium-high heat. Brush the pan with oil (or spray with non-stick cooking spray). Add scant 1/4 cupful batter to the skillet; tilt to coat the bottom of the pan with an even layer of batter. Cook for about 30 to 45 seconds until golden on the bottom, adjusting the heat, as necessary, to prevent burning, Using a spatula, turn the crepe over and cook for 30 seconds. Transfer to a plate. Repeat with the remaining batter.
Stuff each crepe with 1/4 cup of grated cheese and transfer to the prepared backing dish, fitting them snugly into dish. Cove the pan with foil and bake until cheese melts, about 15 minutes.
To serve: Arrange the crepes on a platter and pout the sauce on top. Garnish with corn kernels, Mexican crema and chopped cilantro.