I call this "infidel" lentil soup because I was an unbeliever in lentils, and this soup converted me. It's everything that most lentil soups aren't -- smooth, creamy, an appealing color, almost bisque-like. It's cheap, simple and unfussy to make and can be scaled up or down easily. Even if you don't like lentils, give this one a try.
Step 1: Tools & Ingredients
2 cups red lentils (rinsed several times) - I suppose you could use other kinds, but the orange color of these lentils is so appealing that I won't consider switching.
1 yellow onion, coarsely chopped
water to cover lentils and then some
3 tbsp butter
3 tbsp flour
plain yogurt (I prefer whole - if you have fresh homemade sheep's milk yogurt around, go ahead and use that)
Pot of sufficient size
Blender, stick blender, or fine strainer (that's really the hard way, though)
Bowl or receptacle for lentil puree if it doesn't all fit in your blender
Small pot or electric kettle for boiling some extra water
Step 2: The Lentil Puree
Top off the water - cover the lentils plus about an inch or two, depending on how big your pot is - and bring to a boil.
Chop the onion while that's happening, and add it straight to the pot of lentils.
When your water boils, cut the heat down and let the lentils simmer gently for twenty minutes or so. They should look soft and may look like they're coming apart. Turn off the heat and let them cool for a bit if you have a standing blender, or just jump right in with the stick blender if you're going that way.
Puree the lentils. You need to get all of them out of the pot, so have another receptacle ready if you're using a stick blender or can't fit all of them in your standing blender.
If you're using a strainer instead of a blender, rub the lentils against the holes of the strainer until pureed. That's how my mother-in-law does it. I should warn you that it looks pretty hard core.
Clean the pot of any remaining lentils or onion pieces. Keep the puree handy.
Step 3: The Roux
At this point, boil some water in another pot. A quart is plenty; you probably won't need it all.
Once the butter is melted, add the flour and start stirring. The flour will absorb the butter and turn into a white paste. Continue stirring (you can slow down at this point, but don't stop) until it starts to smell a bit nutty and turns from white to creamy to red-golden. Roux is the French word for this red-golden color as well as the magical substance you've just produced.
Step 4: Bringing Them Together
Into the hot roux, pour a little bit of the lentil puree. It will steam and hiss; stir it vigorously to keep it from burning, as the pot is quite hot at this point, and to prevent lumps. This is why it's necessary to add a little at a time - otherwise you'll have lumps of roux in a thin soup, which is not the idea.
When you've added all the lentils, stirring all the while so as to have a lovely, smooth, thick puree, start adding your boiling water. You're just going to thin the soup out as necessary, and you may not need all of the water, so go a little at a time here, too. Thin the soup more than you think you should, because the roux will continue to thicken it long after you've finished cooking it, and the next day it will be quite thick.
Salt it to taste.
Step 5: Serving
When you serve the soup, it's vital - vital! - to squeeze fresh lemon juice over it. This takes the flavor from pleasant to orgasmic. Yes, I used that word for lentil soup. Don't skip this step.
Optionally, you might also put a nice big spoonful of plain yogurt in the middle as well. This has the additional benefit of cooling the soup a little bit so that you can eat it faster.
Some people like to pour hot melted butter onto the soup; I've tried it, and it makes me want to barf because it's so heavy, but it's an authentically Turkish option.
I also like to serve pieces of toasted and buttered (homemade) whole multigrain bread on the side for dipping. Olive bread, sourdough, or rustic white would also be scrumptious...