Keep a pot with water and salt to boil and place your clean broccoli pieces into the water so that they are submerged completely. Place the timer to 3 minutes to blanch your broccoli and then take out to leave in cold running water or a bowl of ice water to stop the cooking process.
Preheat oven to 350° Fahrenheit/ 180° Celsius.
In a mixing bowl combine the egg, cream, salt, black pepper, Italian seasoning, mustard paste and cheese to a well-combined sauce.
Place cooled broccoli pieces into a large casserole dish. Spread out so that they fit into the whole dish and that they are on a level.
Pour cream sauce mixture all over the broccoli in the casserole dish.
Sprinkle and spread out olive oil over the dish.
Bake cheesy broccoli egg casserole at 350° Fahrenheit/ 180° Celsius for about 30 minutes or until it has a golden crust, it's cooked through and done.
Use fresh or frozen broccoli. Fresh broccoli needs sot be blanched. Frozen broccoli needs to be thawed but I don't blanch frozen broccoli. You can skip step 1, blanching, if you use frozen broccoli. Frozen broccoli is usualy blanched before it was frozen to retain the vital vegetable enzymes.
You can substitute Italian seaosning with your favorite dried herb or herb blend such as oregano, Herb de Provence, Spaghetti Seasoning (yep that does the trick too) or even a mediterranena multi purpose herb blend such as Zaatar.
The addition of Dijon Mustard is optional. It adds some interessting flavors and compliments the broccoli. Besides, mustard is an emulsifier and it will help bind your sauce for the perfect bake.
You can use a good melting cheese that has flavor and that you enjoy. I like to use cheddar, raclette, ementhal, gruyere, and sometimes some parmesan. You can also mix two or three cheese.