This has always remained a beloved choice for our family! Blessings to America!

Preheat your oven to 375°F (190°C).
Bring a large pot of salted water to a boil. Add the broccoli and cauliflower florets and blanch for 3-4 minutes until just tender. Drain and set aside.
In a medium saucepan, melt the butter over medium heat. Stir in the flour and cook for about 1 minute, stirring constantly.
Gradually whisk in the milk, ensuring there are no lumps. Cook until the sauce thickens, about 5 minutes.
Remove the saucepan from heat and stir in the cheddar cheese and half of the Parmesan cheese. Season with salt and pepper to taste.
In a large mixing bowl, combine the blanched broccoli and cauliflower with the cheese sauce. Mix until the vegetables are well coated.
Transfer the mixture to a greased baking dish. In a small bowl, mix the breadcrumbs with the remaining Parmesan cheese and olive oil. Sprinkle this mixture evenly over the top of the gratin.
Bake in the preheated oven for 25-30 minutes, or until the top is golden brown and crispy.
Let it cool for a few minutes before serving.
Variations & Tips
For a bit of spice, add a pinch of cayenne pepper to the cheese sauce. You can also experiment with different cheeses like Gruyère or fontina for a more complex flavor. If you're looking to add some protein, cooked and crumbled bacon or diced ham can be mixed in with the vegetables before baking. For a gluten-free version, use gluten-free breadcrumbs and substitute the all-purpose flour with a gluten-free flour blend.