Working over a gas burner or under the broiler, char the poblanos, turning often until blackened all over. Transfer to a bowl and cover. Let cool 15 minutes then peel, seed and chop.
Preheat the oven to 375°F.
In a small saucepan, melt the butter over medium. Add the shallots and garlic, and cook, stirring often until softened, 1-2 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 and stir until it melts and the sauce thickens, about 1 minute. Add the shredded cheeses and stir until smooth, about 2 minutes. Stir in the mustard and chopped poblanos; remove pan from heat and reserve.
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, chili powder, salt and pepper. Form 6 burger patties or 12 slider patties that are thinner in the center 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, for 7-8 minutes for burgers or 2-3 minutes for sliders.
Reheat the queso over medium heat, stirring occasionally until melted. To assemble, the burgers, top the bun bottoms with lettuce, tomato and chopped onion. Add the patties, chips, some queso sauce, bacon bits and jalapeño rings, set bun tops in place and serve.