Heat oil in a sauté pan. Add garlic and onion and sauté until translucent. Add cumin and oregano and cook for 1-2mins until spices start to toast. Deglaze with beer.
Nestle chicken breasts on top of onions and cover. Cook for 18 minutes. Remove from heat and cool enough to shred the chicken.
Mix the shredded chicken with the onions, garlic and liquid from the pan and add the kernels from 3 ears of corn.
Grill the corn for 15-20 minutes in husks. Cool until it is easy to husk and cut kernels from cob.
At the same time, put poblanos on the grill and char on every side. Put them in a paper sack for 15 minutes to sweat. Remove the pepper skins. They should peel off easily. Stem, seed and dice the peppers.
Melt the butter in a saucepan until bubbly. Add the flour and whisk for 1-2mins until flour is cooked. Slowly add the warm chicken broth. Cook until thickened and add 1 cup Monterey jack cheese and the peppers. Puree and taste for salt and pepper.
Warm up a ladleful of sauce in a small sauté pan and put a tortilla in the pan cooking until pliable.
Place the tortilla on a plate and fill with the chicken mixture and a sprinkling of pepper jack.
Place in a greased 9x13-inch pan.
Continue until all of the filling is used up.
Cover the enchiladas with remaining sauce, sprinkle with the remaining corn and pepper jack cheese.
Cover and bake at 375°F for 35 minutes. Remove the foil and cook for 15 minutes more or until bubbly and golden.