Heat the oil and one tablespoon butter in a 4 quart Dutch oven or pot over medium until shimmering. Add the pancetta, onions, celery, bell peppers and jalapeños and cook, stirring frequently, until the vegetables are soft (about 5 minutes).

Add the remaining 2 tablespoons butter and let melt. Sprinkle the flour and thyme over the vegetables and cook until the vegetables are coated and thickened. Add the beer and stock, and deglaze the pan to scrape up the bits of flour stuck to the bottom. Cook for 5 minutes, then reduce heat to medium-low.

Add the mustard, Worcestershire sauce, and cream, stirring well. Add the cheese 1/2 cup at a time, stirring constantly to ensure the cheese melts, rather than sinks to the bottom. When the cheese is thoroughly combined, taste, and add salt if needed (depending on the stock and cheese you used, you might not need any additional salt, so go lightly at first).