01 -
Add broccoli to a big saucepan with just enough water to cover the bottom (about a cup). Turn heat to high until bubbly, then pop the lid on and cook until broccoli turns vibrant green and tender-crisp, about 4-5 minutes. Drain water, move broccoli to a bowl, and cover it to stay warm.
02 -
Grab a towel and carefully dry the same pan. Melt the butter using medium-low heat. When it's completely melted, sprinkle your flour on top and keep whisking until it turns golden brown, about a full minute.
03 -
Pour milk in gradually while constantly whisking to avoid any clumps forming. Let it bubble gently as you whisk for around 3 minutes until the mixture starts thickening.
04 -
Lower the heat. Add small batches of cheddar, letting each handful completely melt before adding more. Stir in your Parmesan, salt, and the mustard and cayenne if you're using them. Try a taste and add more seasoning if needed.
05 -
You can either drizzle the cheesy sauce over your warm broccoli or gently mix the broccoli right into the sauce before you serve it up.