Parboil the veggies for 5-10 minutes until tender crisp.
In the meantime, combine all the ingredients for the cream sauce in a small saucepan. Heat over medium low heat until very hot, but not boiling, about 10-15 minutes. Stir occasionally to prevent sticking.
Drain the veggies well and spread over the bottom of the casserole dish.
Pour cream sauce over veggies. Stir around lightly to incorporate the sauce throughout.
Combine topping ingredients and sprinkle over veggies.
Bake for 20-30 minutes until bubbly and top top is golden brown.