Late-spring soup the Finnish way

Inspired by the recipe for Kesakeitto (Finnish summer vegetable soup) in Scandinavian Cooking by Sonia Maxwell, I made a new recipe with the ingredients available in my CSA box and my refrigerator stash. Most of the veggies that are considered summer vegetables in Finland are already available garden-fresh in the springtime in Illinois.

For those who are able to tolerate dairy products, I'd recommend using real dairy cream or milk for an even better flavor.

Finnish-style Vegetable Soup
4 to 6 servings

6 small radishes with greens
3 carrots
1 handful spinach leaves
1 small head broccoli
2 Tbsp butter
2 Tbsp flour
1 egg yolk
1 1/2 cups unsweetened almond/soy milk (the traditional Finnish soup uses dairy cream)
2 Tbsp fresh herbs to garnish: dill, parsley or chives (or a mix of two or three of these)

Halve or quarter the radishes. Chop the radish and spinach leaves finely, discarding any tough stems. Cut the carrots into small dice. Cut the broccoli into bite-sized florets. Place radishes, carrots, broccoli into a small pot and cover with water. Cover pot and bring to a boil. Cook very briefly, about 3 minutes. Add radish and spinach leaves and cook 2 minutes. Strain and reserve the cooking water. Set aside cooking water and vegetables. Melt butter in a large pot. Whisk in flour, then slowly whisk in the cooking water from the vegetables and 1 cup of milk/cream and heat just short of boiling. Whisk egg yolk in a bowl with 1/2 cup milk/cream, then add 2/3 cup of the hot soup and whisk. Pour the egg yolk mixture into the soup pot and whisk together. Put the reserved vegetables in the soup pot and reheat. It is important not to heat the soup all the way to a boil, which will curdle the egg yolk. Season with salt and pepper, ladle into serving bowls and garnish with herbs.

Optional vegetable alternatives: new potatoes, peas, small bits of fish or shellfish