In a deep pan, heat stock, salt, pumpkin, onion, garlic, coriander leafs and peppercorns. Bring to a boil, reduce heat to low, and simmer for 30 minutes uncovered. Then puree the soup in small batches (1 cup at a time) using a food processor or blender. In a same pan add butter and dried oregano. When the butter in melted. Then add puree and bring to a boil again. Reduce heat to low, and simmer for another 30 minutes uncovered. Stir in heavy cream.