Peel the onions and slice into rings and then cut each ring open.
Place the bacon in a large saute pan. Place the onions on top and saute the onions until soft and a touch "caramelized" but not brown.
Remove the onions and bacon from the saute pan. Chop the cooked bacon into small pieces. Set aside
NOTE: You can "steam" the onions by heating 2 cups of water in a medium sized saucepan and bring to a boil. Place the onions in a steamer basket over the boiling water and steam for 5 minutes or until soft. But the steamed onions have a stronger onion flavor in this dish.
Place the butter (or dairy free fat) in the saute pan over medium heat until it’s melted.
Add the cooked onions, salt and pepper to the fat.
Saute for 2 minutes.
Remove the pan from the heat.
Add in grated cheese/nutritional yeast.
Whisk in egg yolk, which will thicken the sauce.
Stir in the bacon crumbles.
Plate and garnish with herbs.