In a large saucepan, add fresh broccoli florets and pour enough water to create a thin layer across the bottom. Bring the water to a simmer over high heat, then cover the pan and cook the broccoli for 4-5 minutes until bright green and crisp-tender. Drain and keep warm.

Wipe the saucepan dry, melt 2 tablespoons of butter over medium-low heat until bubbly, then whisk in 2 tablespoons of flour until golden. Slowly add 1 cup of milk and whisk to avoid lumps, simmer for about 3 minutes until thickened.

Reduce heat to low and add 1 cup of shredded cheddar cheese in small handfuls, mixing until smooth. Stir in ¼ cup of grated Parmesan, kosher salt, ground mustard, and cayenne if desired. Adjust seasoning.

Pour the cheese sauce over the warm broccoli or mix together to serve. Enjoy warm!