2 lbs asparagus, trimmed of woody stem bottoms
1 large yellow onion, chopped (1 1/2 to 2 cups chopped)
3 Tbsp unsalted butter
4 cups chicken stock
1 cup water
Leaves of 2 sprigs of fresh thyme
2 Tbsp chopped fresh parsley
1/4 cup heavy cream
A squeeze of fresh lemon juice
Salt and pepper
Cut tips from the asparagus 1 1/2 inches from top and halve tips lengthwise if thick. Reserve for garnish. Chop the remaining asparagus stalks into 1/4-inch rounds.
Melt the butter in a 4 to 5 quart pot on medium heat. Add the onions and cook until translucent, about 5 minutes. Add the chopped asparagus (not the spear tips) to the onions. Sprinkle with salt and pepper to taste. Cook another 5 minutes.
Add the broth, water, and thyme to the pot. Increase the heat to a boil, then reduce to a simmer. Simmer, covered, until the asparagus are tender, 10 to 15 minutes. At the end of cooking, stir in the chopped parsley.
While the soup is cooking, blanch the asparagus tips in a small pot of boiling, salted water (about 1 1/2 teaspoons of salt per quart of water), until the tips are just tender, about 2-4 minutes, depending on the size of the asparagus. Drain. Rinse with cool water to stop the cooking. Set aside.
Use an immersion blender to blend the soup until smooth. (If you use an upright blender, work in small batches, fill no more than a third the blender bowl at a time, and hold down the lid while blending.) Stir in the cream. Stir in the squeeze of lemon juice.
Season with salt and pepper to taste.
Serve with garnish of asparagus tips and homemade croutons.