Turn down heat and simmer until the peas are tender, approximately two to three minutes.
Remove from heat.
Transfer the soup to a blender and add the buttermilk and mint and puree until smooth OR add the buttermilk and mint to the pot with the soup and puree using an immersion blender.
Season to taste with salt and pepper.
Chill for several hours until cold.
To serve, garnish with a dollop of sour cream or plain yogurt and a mint leaf.
Recipe by West of the Loop at https://www.westoftheloop.com/2014/06/16/cold-pea-soup-mint/