In a pan over medium-low heat, heat the grapeseed oil. Add the onions and garlic and caramelize until golden brown, approximately 10 minutes. Deglaze with the beer and let it cook out for 3 to 4 minutes. Add the beef stock, thyme and bay leaf, then bring to a boil. Let simmer for 10 more minutes. Add the butter and slowly incorporate it into the broth so it thickens the broth lightly, about 2 minutes. Season with salt and pepper.
Preheat the broiler.
Fill a small ovensafe bowl with the onion mixture and cover with the Cheddar and Swiss. Melt the top under the broiler until golden, 1 to 2 minutes (or with a kitchen blowtorch). Serve with the toasted baguette.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.
Recipe courtesy of Robert Irvine