As close to Panera's recipe as I could get by taste.
Wild rice expands and sheds starches unpredictably during extended boiling. Simmering the grains for 15 minutes directly in the stockpot releases enough amylose to slightly thicken the base without requiring added cornstarch. Stir the bottom frequently to prevent scorched grains from imparting a bitter taste to the broth.
Adding cold milk directly to a hot pot causes dairy proteins to coagulate and separate. Whisking flour into melted butter in a separate skillet creates a blonde roux that encapsulates the starch granules in fat. Cook this mixture until it turns bubbly and pale gold, ensuring the raw flour flavor vanishes entirely before the dairy enters.
High heat breaks milk emulsions. Keep the stockpot at a gentle medium heat once the dairy and roux are incorporated, never letting the liquid reach a rolling boil after the milk is added. A heavy-bottomed stockpot diffuses direct burner heat evenly, though a standard Dutch oven functions as an effective alternative if stirred constantly.