• In a medium, heavy-bottomed pot, warm butter over medium heat. Once foaming, add chopped onion, stirring to coat. Cook until the onions are lightly golden, stirring occasionally (about 6 minutes). Scoop out half of the onions and set aside.
• Add chicken stock and chopped potato to the pot and bring mixture to a boil over medium-high heat. Once boiling, drop down the heat to medium-low and simmer partially covered for 20 minutes.
• While the broth is simmering, prep the squash blossoms. Break off the stems, peel off the sepals (the small, wavy leaves that grown from the base), and pluck out the stamen. No need to be gentle here. The squash blossoms will eventually be chopped up, so you don't need to keep their original shape in tact. Discard stems, sepals and stamen.
• Divide blossoms into two even piles then slice into 1/4 inch strips (including the bulbous base). Add one pile of slices to the simmering stock and cook for 3 minutes. Carefully blend the mixture until smooth. I used my immersion blender. If you don't have one, use a blender, working batches. Return the mixture back to the pot over medium heat.
• Add the chopped, roasted poblano, milk and reserved onion to the soup, stirring to combine. Simmer the mixture for 10 minutes then add zucchini and corn. Simmer for another 3 minutes, then add the other pile of sliced squash blossoms. Continue simmering for 2 minutes, then take the mixture off of the heat. Stir in crème fraîche and season to taste with kosher salt (I added several pinches).

Serve in soup bowls and finish with a sprinkling of chopped epazote or flat leaf parsley.