Spring Pea Soup with Bacon Croutons

Preheat the oven to 400°. In an enameled cast-iron casserole, combine the onion and olive oil, season with salt and cook over moderately high heat until the onion is soft, 8 to 10 minutes. Add the water and peas and bring to a boil. Cover and simmer over moderately low heat for about 15 minutes.

Meanwhile, spread the bread cubes in a single layer on a baking sheet and bake for 6 minutes, until they just begin to brown. Drizzle the toasted cubes with the melted bacon fat or butter and toss to coat. Return the bread to the oven and bake for 6 minutes longer, until golden brown and crunchy. Set aside.

Using an immersion blender, puree the soup until completely smooth. Alternatively, transfer the soup to a blender and puree, then return to the pot; keep warm over very low heat.

In a small bowl, combine the yogurt with 1/4 cup of the pureed soup. Whisk until smooth. Add another 1/4 cup of the soup and whisk again. Whisk the pea soup–yogurt mixture into the rest of the soup and season with salt and pepper. Ladle the soup into bowls, garnish with mint and bacon croutons and serve immediately.