Romanesco is such a fantastic vegetable! I think it tastes like cauliflower, but a little sweeter. Plus I am always fascinated by the fractal form of it. You could easily make this recipe with just romanesco or cauliflower, but I had both so I went for it!
Start by cutting the romanesco and cauliflower into florettes of roughly even size. That way they will cook at a similar rate.
1-2 heads romanesco and/or cauliflower
2 Tbsp butter
1/4 cup flour or corn flour (fine grind)
1 1/2 cups milk
1/2 cup grated Parmesan, plus more to sprinkle on top
Steam the romanesco and cauliflower until almost tender. They will cook more in the oven, so you want to leave them a little bit firm. I steamed two separate batches and the romanesco took 12 minutes to steam and the cauliflower only took 10 minutes.
Make the Béchamel sauce. Melt the butter over medium-low heat then whisk in the flour to make a roux. Add 1/2 cup milk, whisking constantly. Whisk until the lumps dissolve and you have a smooth, thick paste. Add the remaining milk, 1/2 cup at a time. Each time you should whisk until the sauce thickens.
When the sauce has thickened (roughly the consistency of gravy), stir in the Parmesan, white pepper, and salt to taste. Remove sauce from heat.
Place half of the florettes on the bottom of your baking dish, sprinkle with Parmesan, and follow with half of the Béchamel sauce.
Put the remaining half of the florettes on top of the first layer and cover with the remaining Béchamel sauce and sprinkle with Parmesan.
Bake in a pre-heated 350 degree oven until golden brown, about 30 minutes.