Instructions: Remove the tough outer layers of the fennel bulbs, split the bulbs lengthwise, and cut them crosswise into 1/4-inch-thick slices.

Peel off the outer layer of the leeks, and trim off the root ends and the dark green tops. Split the leeks lengthwise and cut the leek halves crosswise into 1/4-inch slices. Plunge the slices into a bowl of cold water to rinse off any sand. Lift the leeks out of the water, leaving the dirt to sink to the bottom of the bowl.

Melt 1 tablespoon of the butter in a large saute pan over medium heat. Add half the fennel slices and cook until they are soft, about 5 minutes. Season with salt and pepper and transfer to a large bowl. Cook the rest of the fennel until soft with another tablespoon of the butter and add to the bowl. Then cook the leeks the same way, in two batches with the rest of the butter, and transfer them to the bowl.

Preheat the oven to 375 degrees.

Pick the leaves off the parsley and thyme sprigs and chop them. Toss the herbs together in the bowl with the fennel and leeks. Taste, and add more salt and pepper if necessary. Put the vegetables into a shallow ovenproof dish and pour over just enough of the cream and the vegetable or chicken stock to barely cover them. Bake the gratin in the oven for 45 minutes to 1 hour, checking every 15 minutes or so to make sure the cream is still covering the vegetables. If the top of the gratin appears to be drying out, push the vegetables down with the back of a spoon, drizzling a little more cream over the top. The cream will bubble up around the vegetables, and the top will brown nicely. Serve hot.

This recipe yields 6 servings.

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