Prepare the vegetables by blanching them. Bring a pot of water to a boil on the stove top and let the vegetables cook for 5 minutes. Drain the water and transfer the vegetables to a pot of ice-cold water to stop the cooking process.
Prepare the sauce:
In a saucepan on the stovetop, heat the olive oil and add the garlic. Let the garlic sauté for a couple of minutes, until it loses its raw taste. Take the pan off the heat and add the flour, whisking it around.
Add the milk slowly, whisking continuously. Ensure that there are no lumps in the sauce. Return the pan to the heat and cook on low heat for 3-4 minutes until the sauce has thickened. Add the grated cheese (gruyere or parmesan and cheddar). Add salt to season and stir to combine. Keep this aside while you prepare the baking dish.
Butter the inside of an oven-safe baking dish (you can use olive oil as well). Transfer the vegetables to the baking dish. Pour the sauce over the vegetables.
Prepare the Crumb Topping:
Mix together the bread crumbs, cheddar and melted butter. Spread this topping over the vegetables and sauce.
Cover the dish with foil and bake in the oven at 180 C for 20-25 minutes until the crumb topping starts to turn golden brown and the sauce begins to bubble from the sides. Let the dish rest for 10 – 15 minutes before serving.
Notes
This dish is great for prepping ahead and freezing. Assemble the veggies and sauce and topping and freeze the dish for upto 1 month. You can thaw and bake the dish when you're ready to have it for a meal. Asparagus is a seasonal vegetable, so you could made the dish with substitutes all through the year. Use vegetables with similar cooking times - carrots, corn, green beans are great subsititutes.