In a medium pot over medium-low heat, melt the butter.

When butter is melted, add the flour and salt and stir until it comes together in a thick paste.

Add 1 cup of milk and whisk until all the lumps are gone.

Add the other 3 cups of milk and turn up the heat to medium-high. Continue to whisk until soup thickens, making sure to scrape the bottom as you stir.

Add your steamed broccoli, stir, and serve.