Preheat oven to 375F; spread 1/2 cup enchilada sauce out in the bottom of each of two 2-quart casserole dishes.
Heat the oil in a medium skillet over medium heat; add the poblano pepper, onion, and garlic, and cook until softened, but not browned, about 5 to 7 minutes, stirring occasionally. Stir in 1/2 cup enchilada sauce and cream cheese and whisk until smooth.
Pour the creamy onion/poblano mixture into a large bowl and stir in the turkey, black pepper, cilantro, scallion, and 1/3 of the shredded white cheddar.
Place about 3 tablespoons of the filling length-wise onto a slice of turkey breast and roll it up. Place it seam-side-down into the prepared casserole dish and repeat this process until you run out of filling or sliced turkey (you should have enough to fill up the 2 casserole dishes).
Spread 1/2 cup enchilada sauce on top of the enchiladas in each dish, and divide the remaining cheese on top.
Bake until the cheese is melted and the enchiladas are warm throughout, about 20 minutes.
Sprinkle on additional scallion and cilantro if desired, and serve.