Mac and cheese with bacon and caramelized onions

olive oil

onions (, medium or large, sliced)

salt

balsamic vinegar

strips bacon (or prosciutto or pancetta)

elbow pasta

heavy cream

milk

white Cheddar cheese (, freshly shredded )

Gruyere (, freshly shredded)

salt (or more – to taste)

cayenne pepper (to taste)

paprika (to taste)