But just because it's comfort food, it doesn't mean you can't up-scale it a bit. Porcini mushrooms and a bit of truffle add that magical touch to this recipe. Meanwhile, the mushrooms take center stage, so there's no need for meat - this is a vegetarian gravy.
The truffle oil is used to finish the dish - and a little goes a long way. A few drops per serving is more than enough. If you prefer a more subtle truffle flavor, porcini and truffle-flavored oil is a nice option.
For very smooth potatoes, use a ricer or food mill rather than mashing. If you don't have either of those tools, you can still get smooth potatoes with a regular potato masher. Make sure the potatoes are fully cooked, and then mash them on their own, before you add butter or other additions.
Some folks like to use an electric mixer to beat their potatoes, but I'm not one of them. Over-mixing can lead to gluey potatoes, and that's not something I want to risk - I'd rather find a few bits of un-mashed potato.
Also, beating potatoes with an electric mixer brings back the horrifying vision of the green-flecked mashed potatoes I made when I was a kid. I used mom's electric hand-held mixer to beat the potatoes in the same pot she cooked them in. Unfortunately, it was a teflon-coated pan. Thus, the green flecks. It took us a while to figure out what happened, and it's not something I ever care to repeat.
Decadent Mashed Potatoes and Mushroom Gravy
1 ounce dried porcini mushrooms
2 tablespoons unsalted butter
1/2 pound baby portabella mushrooms, sliced
2 tablespoons flour
1/2 teaspoon fresh thyme leaves
Salt, as needed
For the potatoes:
2 pounds yukon gold potatoes
4 tablespoons unsalted butter
1/4 cup sour cream
1/4 cup heavy cream
1/4 teaspoon freshly ground white pepper
Salt, to taste
Milk, as needed
To make the gravy:
Put the dried porcini mushrooms in a saucepan with water just to cover. Bring to a boil, then lower to a simmer and cook for 20 minutes. Add more water, if needed, to keep the mushrooms barely covered.
Strain the liquid through a coffee filter or through a paper towel in a strainer. Reserve the liquid. Rinse the mushrooms and chop finely.
Meanwhile, melt the butter in a saute pan. Add the sliced portabella mushrooms and a pinch of salt. Cook until the mushrooms begin to lose their water. Add the diced porcini mushrooms and cook, stirring as needed, until all the liquid is gone. Add the flour and stir until you don't see any dry bits of flour.
Add the reserved mushroom cooking liquid, plus water to equal two cups. Stir well. Bring to a boil, then lower to a simmer. Cook for at least 10 minutes to cook out the raw flour taste, stirring as needed. Continue cooking until the gravy has thickened to your desired consistency. Keep in mind that it will be thinner when it's simmering than it will be once it's off the heat. If you need to thin the mixture, add water as needed.
Add the thyme leaves and stir to combine. Taste for seasoning and add more salt, if desired.
To make the potatoes:
Peel the potatoes and cut into cubes. Add to saucepan with cold water to cover. Add 2 teaspoons salt. Bring to a boil, then lower to a simmer. Cook until the potatoes are tender, then drain well.
Pass the potatoes through a ricer or food mill, or mash with a potato masher. Add the butter, sour cream, cream, and pepper, and stir to combine. Different potatoes will absorb liquid differently, so if the potatoes still seem dry, add milk, a little at a time, until you get to the consistency you desire. If you add a little too much liquid, heat the potatoes gently, stirring, to thicken the potatoes again.
Serve the potatoes with the gravy. Add a few drops of the truffle oil to finish each serving. Or, if you're passing the potatoes and gravy separately you can drizzle the oil into the gravy before serving.