2 weeks away from Cancale and I come home to a bare fridge on a national holiday (May Day). Meaning: any attempt to shop is pretty pointless. There may be a small grocery open this morning where I could buy essentials—bread, cheese, eggs (oh wait, I still have some of those in the fridge), a head of lettuce, a handful of vegetables. But when a full-out, favorite market is just 24 hours away, these prospects seem bleak, and not really worth the effort.

Times like these are times for potato-onion soup. I have potatoes, I have onions…and I have the recollection of a luscious version my neighbors shared with me one time when I returned from a previous journey. Their soup was a dun brown, the strange color due to the very thing that made it special: caramelized onions. Those onions, however, gave the soup a flavor so rich, so complex, and so satisfying that I forgot all about the (somewhat unappetizing) color. I’ve craved the soup ever since but worried my version wouldn’t live up to the memory of the original.

Miraculously, it does—and in just three ingredients (four if you count the optional thyme). And once you overlook the soup’s color, it turns out to be very thing for a May Day that still hasn’t yet shaken the chill of winter.

3-Ingredient Potato and Caramelized Onion Soup

2 Tbs. (30 g.) butter or olive oil
1 lb. (500 g.) onions, peeled, halved and thinly sliced
1 lb. (500 g.) potatoes, such as russet or Yukon gold, peeled and thinly sliced
1 sprig fresh thyme, optional

MELT the butter in a large saucepan over medium-low heat. Add the onions, and sprinkle with salt. Cover, and cook 30 minutes, stirring every 5 to 7 minutes, until the onions are very soft and browned and have begun to stick to the bottom of the pan.

STIR in 3 ½ cups (900 ml.) water, using a wooden spoon or spatula to scrape up any stuck-on bits from the bottom of the saucepan. Add the potatoes and thyme, cover, and simmer 30 minutes, or until the potatoes are very soft.

BLEND the soup in a blender or food processor, or with a handheld blender, until smooth. Season with salt and pepper. Makes 6 cups