Bhutan's mountainous, so their food is meaty. There are potatoes and cheese too. But the distinctive part is the chilies. There are chilies in everything. They're not super spicy, as hot peppers go, but they're ubiquitous. Their most famous dish, Ema Datsi, is just chilies in cheese. I've had meals of ema datsi, beef with chilies and cheese, pork with radish and chilies, soup with chilies, and pickled chili paste on the side.
If that sounds terrible, never fear, and if that sounds great, read on. The trick about Bhutanese food is that you won't get any by default. For each meal, you're herded into the tourist room, and all you white people are served a sumptuous buffet of vaguely-Asian dishes. Stir fried vegetables, some beef or chicken, noodles, maybe fried rice or momos. Meanwhile, your guide and driver are in the other room, eating their everyday (delicious) Bhutanese food! I guess they figure that tourists will want the more familiar stuff. So the secret is, if you want Bhutanese food, ask your guide if you can eat with them. It's an unusual request, I guess, so be very clear ("yes, I actually do want to eat Bhutanese food, like the kind you're eating, and yes, I like spicy food"), and they'll let you. It's more fun too, especially if you're alone. Eating alone in an empty room is weird.
Anyway, more about the food: they sometimes drink butter tea, like the Tibetans, and sometimes buttermilk (whey). They eat a lot of red rice, which is short grain and only a little sticky. They use the whole animal: dishes like pigs' feet show up sometimes. Dried meat and dried fish are popular as well. And they eat a lot. "We Bhutanese are good in eating! Not so good in working," laughed one guide. I have to disagree about the working, but it's true that I often found myself quite stuffed.