Sopa de Chile Poblano (Poblano Chile Soup)

Ingredients

• 2 pounds poblano chiles
• 6 tablespoons unsalted butter
• 1 white onion large, roughly chopped
• 1 rib celery roughly chopped
• 1 medium carrot roughly chopped
• 4 ounces spinach roughly chopped
• 1/3 cup parsley minced
• 4 cups chicken stock
• 2 cups milk
• 1 cup heavy cream
• kosher salt
• freshly ground black pepper
• 1/2 cup crema or sour cream
• 1 serrano chile stemmed, seeded, and minced
• fried tortilla strips to garnish, optional