Peel and thinly slice the yellow onions. Heat olive oil in a skillet and cook the onions for 40-50 minutes until caramelized.

Wash and chop the Yukon Gold potatoes, then boil in a pot until fork-tender.

Drain the potatoes, then mash them with butter, half & half, and kosher salt until creamy.

Fold in half of the caramelized onions and Parmesan cheese, mixing thoroughly.

Transfer mashed potatoes to a bowl, top with remaining onions, and garnish with herbs.