Begin by warming the onions. Slice them and place in a pot with butter and a pinch of salt.
Allow the onions to develop a slight char on the bottom, then deglaze the pot with water.
Repeat this process until the onions are nicely caramelized, which should take about 15 minutes.
Next, add the garlic, fresh rosemary, and thyme to the pot, toasting the aromatics for about a minute.
Pour in the beef broth and then add the pasta.
Bring the mixture to a simmer and cook for approximately 10 minutes, or until the pasta is fully cooked.
Stir in the milk, Gruyère, and cheddar cheese until everything is melted and well combined.
Finally, add a can of rinsed white beans and top with bacon bits if desired.
