Heat water to boiling in a deep skillet or saute pan with a lid over medium heat. Add broccoli florets and cover to steam for 3-5 minutes. Transfer to a serving dish and cover to keep warm.
Melt butter in a medium saucepan or skillet over medium heat. Add flour and whisk constantly until completely combined, then cook, whisking often, until golden; 2-3 minutes.
Pour in milk and bring to a simmer. Let simmer for 3-5 minutes or until mixture is thickened. Stir in cream cheese and ground mustard.
Remove from heat and cool for a few minutes before stirring in shredded cheddar. Taste and add salt and pepper as desired. If the sauce is too thick, stir in a little bit of warm milk until the right consistency is reached.
Pour over steamed broccoli and serve.
Broccoli with Cheese Sauce https://www.yellowblissroad.com/broccoli-with-cheese-sauce/