In a large bowl, combine corn masa, chicken broth, softened butter, baking powder, and salt. Mix until a soft, pliable dough forms.
Divide the dough into golf ball-sized portions and press each one into a thin disc.
In a mixing bowl, combine shredded cooked chicken, roasted and diced poblano peppers, corn kernels, shredded Monterey Jack cheese, chopped cilantro, ground cumin, salt, and pepper. Mix thoroughly.
Place a spoonful of the filling in the center of each tamale dough disc.
Fold the sides of the dough over the filling, creating a sealed packet.
Arrange the tamale packets in a steamer basket and steam for 25-30 minutes or until the dough is cooked through.
In a saucepan, melt unsalted butter over medium heat. Add all-purpose flour and cook, stirring constantly, until golden brown.
Gradually whisk in chicken broth and continue stirring until the mixture thickens.
Add ground cumin, salt, and pepper to taste. Simmer the sauce for 5 minutes.
Preheat your oven to 375°F (190°C).
In a baking dish, layer the steamed tamales with the luscious sauce.
Bake for 15-20 minutes or until the stack is golden and bubbling.