Roast a whole garlic bulb for 1 hour using this method or drizzle individual cloves with olive oil and salt and bake at 350 until soft (about 15 minutes).

Meanwhile, bring a large pot of salted water to a boil.

Add the potatoes and the cauliflower (I did them at the same time) and boil until knife-tender (until you can poke with a knife and it easily slides out). My cauliflower took about 15 minutes, while my potatoes took 25-35.

In a food processor, puree the cauliflower with roasted garlic, 2 tablespoons of olive oil, rosemary, and a few generous pinches of salt and pepper. Taste and adjust seasonings. (Tip: this mixture can be over-flavored because it'll get mixed with the potatoes later).

When the potatoes are soft, remove them from the pot. Peel them (careful, they’re hot) and use a food mill, ricer, or masher, to mash them.

Add 2 more tablespoons of olive oil, then stir the cauliflower puree into the bowl with the potatoes.

Stir in a folding motion until smooth and creamy. If necessary, add ¼ cup (or so) of hot starchy potato water to help it out.

Taste and adjust seasonings, adding more olive oil, salt, pepper, and/or rosemary to taste.

Serve hot. Mine actually reheated great too - store in the fridge, microwave the next day.