Step one. Melt the butter in a large pot over medium-high heat. When the butter begins to foam, add the onions, mushrooms, garlic, and a pinch of salt. Saute for 5 minutes, stirring often.
Step 02, Sprinkle in the flour, coating the mushroom mixture. Cook for 1 minute, while stirring constantly. The flour may start to stick to the bottom of the pot, so be careful not to scorch it.
Next step is, Gradually stir in the broth, scraping up the bits from the bottom of the pot. Pour in the milk and bring to a boil over high heat. Reduce the heat to simmer for 8 to 10 minutes, stirring occasionally.
