Working over a gas burner or under the broiler, char the poblanos, turning often, until blackened all over. Transfer to a bowl. Cover; let cool 15 minutes. Peel, seed and chop the poblanos.
Preheat the oven to 375 degrees .
In a small saucepan, melt the butter over medium. Add the shallots and garlic and cook, stirring often, until softened, 1 to 2 minutes; season with salt and pepper. Stir in the cornstarch. Add the milk and cook, stirring often, until it comes to a bubble. Add the cream cheese; stir until it melts and the sauce thickens, about 1 minute. Add the cheeses; stir until smooth, about 2 minutes. Stir in the mustard and poblanos; remove from the heat. Just before serving, reheat the queso over medium, stirring occasionally, until melted.
Arrange the bacon on a slotted broiler pan or a parchment-lined rimmed baking sheet. Bake until browned and crispy, about 20 minutes, then chop.
In a medium bowl, combine the sirloin, onion, Worcestershire and chili powder; season with kosher salt and pepper. Form into 6 burger patties or 12 slider patties (thinner in the centers for even cooking).
Heat a cast-iron skillet or griddle pan over medium-high. Add the canola oil, one turn of the pan. Add the patties and cook, turning occasionally, 7 to 8 minutes for burgers or 2 to 3 minutes for sliders.
Top the bun bottoms with lettuce, tomato and chopped onion. Add the patties, chips, queso sauce, bacon bits, jalapeno rings and bun tops.
