Melt the butter in a pot and saute the onion until translucent.

Add the cauliflower, potatoes, and broth and simmer 20 minutes until the potatoes are fork-tender.

Mash about half the vegetables in the pot to thicken, leaving some chunks.

Stir in the milk and shredded cheddar until melted and creamy.

Season with salt and serve hot, leaving it a little chunky.