Part 3/7:
Before building the sauce, finely chopping onions ensures that the soup remains smooth without chunky bits. Sautéing the onions in melted butter adds depth and sweetness, forming the foundation for the cheese sauce. Then, a classic roux—equal parts butter and flour—is cooked carefully to avoid raw flour flavor. Whisking in milk, along with a touch of Dijon mustard, hot sauce, and white pepper, enriches the mixture while maintaining a balanced, flavorful profile.