Melt butter in large, heavy pot over medium-high heat. Sweat onions, and stir in the flour until incorporated. Gradually whisk in the stock. Add the broccoli and bring to a simmer. Cook for 20 minutes. Finish with cream. Roughly puree with an immersion blender and season, to taste, with salt and pepper.
Per Serving (based on a 6-serving yield): Calories: 217; Total Fat: 16.5 grams; Saturated Fat: 10 grams; Protein: 6 grams; Total carbohydrates: 12 grams; Sugar: 2 grams; Fiber: 3 grams; Cholesterol: 48 milligrams; Sodium: 186 milligrams