Cardoons au Gratin / Radicchio au Gratin

What to do with leftover Bagna Cauda vegetables? Gabriel grew up eating cardoons au gratin every winter in Geneva, Switzerland. When I tried it the first time I found that the dish, while very substantial, was nowhere near as heavy as potatoes au gratin, this is a green vegetable after all. The bitterness of red radicchio pairs beautifully with a rich cheese sauce, so I’m making 2 gratins today. The cardoons were boiled for 30 minutes (yes! This veggie that resembles celery really does need that much cooking. My last gratin of cardoons (pre-boiled for 20 minutes) was very unpleasantly al dente). The radicchio was raw going into the oven. I make a béchamel sauce with melted cheese (sauce mornay) for the vegetables and topped the casseroles with toasted bread crumbs. Gruyere and fontina are perfect for this dish but you can experiment with other medium hard cheeses. I’ve just tried a Greek kefalotiri which is very hard and very salty. I added no extra salt to my dishes and they turned out well.
Cardoons or red radicchio au Gratin:
2 cups of pre-boiled (30 minutes) cardoons cut into 3-4 inch pieces OR 1 large head of radicchio cut into 1 in crosswise slices (about 3 cups loosely packed)
1 tsp unsalted butter
1-2 tsps flour
2 cups milk
½ cup grated cheese
1 tbsp unsalted butter
½ cup dry bread crumbs
Pre-heat oven to 400F. Place the vegetables in a 9” x 13” shallow oven dish. Melt 1 tsp of butter in a medium saucepan. Add the flour and stir to create a homogeneous, bubbling roux. Cook for 1 minute then add the milk slowly. Stir vigorously to incorporate the milk and to smooth the inevitable lumps that form at the beginning. Cook for 5 minutes until thick and totally smooth. Add the grated cheese and continue stirring until the sauce returns to the same smoothness as before. Pour evenly over the vegetables. Melt 1 tbsp of butter in a frying pan and add the bread crumbs. Mix until the butter is evenly absorbed and then toast until the bread crumbs get one shade of brown darker. Sprinkle bread crumbs evenly over the casserole with a large spoon. Bake for 30 minutes or until bubbly in the middle.