Melt butter in a saucepan over medium heat. Add shallot, salt and pepper and cook until softened, about 5 minutes. Sprinkle flour over and cook, stirring constantly for 2 minutes. Gradually whisk in vegetable broth and bring to a boil.

Add broccoli and reduce heat to low. Cover pan and simmer for 5 to 7 minutes, or until broccoli is tender. Remove from heat and stir in cheddar and Parmesan cheese until completely melted.

Season, to taste, with additional salt and pepper and serve garnished with extra cheddar cheese.