Melt the butter in a large saucepan over medium heat. Stir in the flour and cook until the flour has turned golden brown, about 3 minutes. Whisk in the vegetable stock and bring to a boil over high heat. Whisk in the pumpkin puree until no lumps remain, then add the chipotle peppers, half-and-half cream, sofrito, Worcestershire sauce, salt, and paprika. Return to a simmer, then reduce heat to medium-low, and cook for 8 minutes until thickened and hot.