2) Melt one tablespoon butter in a large frying pan over medium heat. When it foams, add onion, season well with salt and freshly ground black pepper, and cook until softened, about one minute. Add spinach and cook until spinach is well wilted, about two minutes.
3) Place bacon on bottom of ramekins and top with spinach. Crack eggs into ramekins, place one tablespoon of cream over each egg, and divide half of cheese evenly among ramekins.
4) Put ramekins on a baking sheet and bake, rotating pan halfway through baking, until whites are just set but yolks are still runny, about 15 to 18 minutes.
5) Meanwhile, spread remaining two tablespoons butter on four slices of sourdough bread. Top with grated cheese and toast until golden brown. Serve eggs with toast.