Active preparation time: 25 minutes
Total time: 35 minutes
Serves: 4
2 large white onions
4 Tbs (½ stick) unsalted butter
2 cloves garlic, sliced
1 bay leaf
1 Tbs fresh thyme, chopped
1½ cup (12 fl oz/355 ml) dry Irish stout
1 qt (32 fl oz/946 ml) unsalted beef broth
Kosher salt
Black pepper
4 thick slices of sourdough or French bread
8 slices of Gruyère cheese