The September soup.

Potato, leek, and the last of the green, stirred in off the heat so it stays green. One pot. Written for nine thousand feet, where the water boils cooler and everything takes a little longer, which is the point of September anyway.

What you need

• 3 tablespoons butter
• 3 leeks, white and pale green only, sliced into rounds and washed twice, because grit hides in leeks the way it hides in most things that look clean
• 1 yellow onion, chopped
• 2 cloves garlic, sliced thin
• 1½ pounds Yukon Gold potatoes, peeled and cut small so they give up quickly
• 5 cups chicken or vegetable stock (at altitude: 5½)
• 1 bay leaf and a few stems of thyme, tied if you are tidy
• fine salt and black pepper
• 4 big handfuls of the last green you have: spinach, chard, the tender part of kale, stems out (this is the leaf in front of the camera)
• ½ cup cream, or a spoon of plain yogurt in each bowl instead
• half a lemon
• a little olive oil and some chives to finish

What you do

1. Butter in a heavy pot over medium low. Leeks, onion, a good pinch of salt. Cook them slowly, ten minutes, stirring now and then, until they are soft and sweet and have not browned. Browning is a different soup. Not a worse one, but not this one. Garlic for the last minute.
2. Potatoes, stock, bay and thyme. Bring it up to a simmer, put the lid on, and let it go until a potato falls apart when you press it against the side with a spoon: about twenty minutes at sea level (at altitude: thirty to thirty-five, and leave the lid on).
3. Fish out the bay and the thyme stems. Blend it smooth, in the pot with a stick blender or in batches with the lid cracked. Taste for salt now, before the green goes in, because the green will hide it.
4. Off the heat. Stir in the greens by the handful until they wilt into it, about a minute, then blend again, briefly. Off the heat is the whole recipe. Greens cooked in a boiling pot go the color of a November lawn. Stirred into a hot pot that is no longer on the flame, they stay green, and so does the soup.
5. Cream, a squeeze of lemon, pepper. Stir. Do not let it boil again.
6. Bowls. A thread of olive oil across the top, chives if you have them. Bread. A lamp.

The house standard

The color of the leaf in front of the camera, not the hillside behind it. Smooth enough to hold a spoon, thin enough to drink from the bowl when nobody is looking. The lemon should be felt and not found.

If it is grey, the greens went in too early. Make it again; it is a Tuesday.

It is better the next day, like most soups and some people, but it will have lost a little of the green. Warm it gently and add one more handful, off the heat, and it comes back.

There are things you cannot feel until you have briefly been without them. Warm hands. A quiet room after a loud one. Someone expecting you.

Soup, probably. I have become old enough to be emotionally affected by soup. This was not in the brochure.