Heat the oven to 425°F with a rack in the middle. Set a 2-quart baking dish near the stove so it is ready when you need it.

Fill a large pot with water and bring it to a boil over high heat. Add 1 teaspoon of the kosher salt to the water.

Put the broccoli florets into the boiling water. Cook for 2 minutes, until the broccoli is bright green and just starting to soften.

Use a slotted spoon to transfer the broccoli from the pot to a colander. Leave the water boiling in the pot.

Add the orzo to the same pot of boiling water. Cook it for about 6 to 7 minutes, or 2 minutes less than the package directs, so it is mostly tender with a little firmness in the center.

While the orzo cooks, put a large saucepan or deep skillet on the stove over medium heat. Add the butter and let it melt.

Add the chopped onion to the saucepan with the remaining 1/2 teaspoon kosher salt and the black pepper. Cook for 4 to 5 minutes, stirring often, until the onion is soft and no longer looks raw.

Sprinkle the flour over the onion in the saucepan. Stir for 1 minute, until the flour coats the onion and you do not see dry patches.

Pour the vegetable broth into the saucepan slowly while whisking. Keep whisking until the mixture looks smooth.

Pour the milk into the saucepan and stir in the Dijon mustard. Bring the sauce to a gentle simmer and cook for 3 to 4 minutes, stirring often, until it thickens enough to lightly coat a spoon.

Stir the lemon zest, 1 cup of the fontina, and 1/4 cup of the Parmesan into the saucepan. Stir until the cheese melts into the sauce.

Add the drained chickpeas to the saucepan. Cook for 2 minutes, stirring gently, until the chickpeas are hot.