Spring Vegetable Soup with Sour Cream and Fresh Dill

Name: Spring Vegetable Soup with Sour Cream and Fresh Dill
Ingredients: 1 tablespoon butter; 1 tablespoon olive oil; 1/2 cup diced white or yellow onion; 1/3 cup diced peeled carrot; 1/3 cup diced celery; 1/2 teaspoon kosher salt; 3 garlic cloves, minced; 6 cups chicken stock, preferably home-made; 3/4 pound red-skinned potatoes (about 3 medium); about 4 medium carrots (1 c. sliced); about 1 bunch asparagus (2 c. chopped); 2 cups frozen petite peas, unthawed; sour cream, for serving; 3 tablespoons chopped fresh dill, for serving