Chilled Pea Soup with Fresh Mint

In a 6-quart Dutch oven, melt butter over medium-low. Add onion, salt and pepper. Cook, stirring occasionally, until softened but not browned, 6 to 8 minutes.

Add chicken broth. Bring to a boil. Add peas and return to a boil. Cook just until peas are tender, 2 to 3 minutes.

Remove from heat; add mint and buttermilk. Let cool slightly. Transfer mixture to a blender, working in batches as necessary, and puree until smooth.* Cover and chill soup at least 6 hours or overnight. Serve cold. If desired, garnish with chives.