Steam the broccoli and cauliflower in the soup pot (or however you wish) until slightly firm with good texture and color.( about 8 minutes on high heat)
Do NOT cook them to mushiness.
Remove the veggies and Set aside.
Making the sauce- In a large soup pot, melt the butter on low heat.
Raise heat to medium and add the flour.
Whisk the flour and butter together until it bubbles and immediately pour in 1 cup of milk while whisking.
Add the remaining milk slowly as the sauce thickens, whisking constantly. Add shredded cheeses into the sauce.
Stir until all the cheese is melted. Pour the steamed vegetables/ Bring up to slow boil over medium heat while stirring to thoroughly mix the ingredients.
REDUCE the heat to simmer stirring often.
When veggies are tender, ladle into a bowl and serve!