Bechamel Sauce

Melt butter in medium saucepan over medium heat until foaming; add flour and cook, whisking constantly, until thoroughly combined, about 1 1/2 minutes; mixture should not brown. Gradually whisk in milk; increase heat to medium high and bring to full boil, whisking frequently. Add salt, reduce heat to medium-low, and simmer 10 minutes, stirring occasionally with heatproof rubber spatula or wooden spoon, making sure to scrape bottom and corners or saucepan. Transfer bechamel to bowl and cool until just warm to the touch, about 30 minutes.