BEET, RHUBARB, AND GINGER SOUP

Steps:

• Break or cut each rhubarb stalk into 2 or 3 pieces, just so they fit in the saucepan, and set aside. Wash the beets, remove the stalks and leaves (see p.199 for what to do with them), and trim each beet, cutting away the barnacly bits; there's no need to peel. Roughly chop into ¾-inch chunks. Peel the onion and roughly chop it.
• Warm the oil in a decent-sized saucepan or Dutch oven that comes with a tightly fitting lid-I use one of 10 inches diameter-and cook the onion for about 10 minutes over medium-low heat, stirring frequently. It won't soften much in that time, but enough for now.
• Peel and roughly chop the garlic, and stir it into the pan of onions. Cook for about 2 minutes, then stir in the cumin and tumble in the rhubarb and beets. Add the water and salt, turn the heat to high and bring to a boil. Once it's bubbling, turn the heat down, clamp on the lid, and let it all cook at a robust simmer until the beets are utterly, utterly soft. This always takes more time than you'd think: I'd reckon on 1½ hours, though it easily could take longer.
• With a stick blender (and if yours comes with a soup-blending attachment, so much the better), blitz until you have a smooth and velvety ruby soup.
• If the skin's tough, peel the ginger with the tip of a teaspoon, then coarsely grate it onto a plate. Moving fast, get out a piece of paper towel and spoon half the grated ginger into the center, then bring together the edges of the paper and twist. Holding this little swag bag over the soup, press on it to squeeze out the intense juice. Now get another square of paper towel, and do the same with the remaining half of grated ginger. Taste for seasoning, ladle out into waiting bowls, and drizzle over each a little horseradish cream or green tahini sauce as you wish.