Melt
2 tablespoons of butter with the oil in a large
saucepan over low heat. Add the onion, garlic,
parsley, and basil and cook for 5 minutes.
Add the zucchini and season with salt and pepper.
Cover and cook for about 20 minutes, adding 2-3
tablespoons of water if the mixture dried out to
much.
Uncover, turn up the heat, and stir until the
vegetables are coarsely mashed and any excess liquid
has evaporated.
Preheat the oven to 350°F/180°C/gas 4.
Butter a 1 1/2-quart (1.5-liter) ring mold.
Melt the remaining butter with the flour in a small
saucepan over low heat. Cook for 1 minute, stirring
constantly.
Remove from the heat and pour in half the hot milk.
Return to the heat and cook until the mixture
thickens. Gradually mix in the remaining milk,
stirring constantly. Season with salt and pepper and
add the nutmeg.
Cook for
5-10
minutes, stirring constantly, to make a creamy
Béchamel sauce.
Stir in the cooked vegetables and mix well.
Add the eggs, beating until just blended.
Mix in the Parmesan.
Pour the mixture into the prepared mold.
Bake for about 1 hour, or until light gold and set.
Let cool for 15 minutes.
Turn out onto a serving dish and serve in slices.