Method: In a double-boiler of water, steam prepared broccoli; until al dente. Remove from steamer and leave aside; covered. Heat a large cooking pan on high. Melt butter and add oil. Stir in flour until colour slightly changes. Away from heat; pour milk while stirring, forming a creamy emulsion that is lighter in consistency than whisked yoghurt. Season, add cheese and cream. Bring to a preboil and remove away from heat. Place broccoli in a serving dish. Gently pour hot cheese sauce over and serve. Place some extra grated Parmesan aside in a separate small bowl; for optional sprinkling on top of individual servings.