Preheat oven to 400°F
Cut florets from broccoli stalk and cut up cauliflower as well. Next steam the broccoli and cauliflower seperatly. Steam them until they are semi soft. They should still have a crunch when you pull them off. Set them to the side.
Chop and cook bacon, then set aside.
In a pot saute the onions in a little oil. When they have softened toss in butter and minced garlic and cook until fragrant. Next pour in heavy cream and add in cream cheese. Heat should be medium. Do not let the sauce come to a boil. If it begins to simmer reduce the heat, it should only steam or a little simmer while preparing.
Stir the heavy cream and cream cheese until cream cheese melts down smoothly. Once smooth and melted add in stock, mayo and lemon juice. Stir everything in smoothly. Now salt and pepper the sauce to taste.
In the casserole dish lay out broccoli and cauliflower and make sure it's even across and pieces aren't too large. Pour cream sauce over then mix everything together. Sprinkle bacon across and then cover with shredded cheese.
Bake for 25-30 minutes checking for browning of the cheese. Remove, allow to cool then serve.
***Note*** the garnishing you see is only parprika. It does nothing for flavor. I sepreated the casserole into 9 serving because I used a square dish.