This is a rich, magnificent dish, so enjoy it and don't even think about replacing the heavy cream with anything else or skimping on the amount. A sprinkle of lemon zest at the end gives it a bright pop.
Source: Martha Stewart Living, March 2012
Prep Time 25 minutes
Total Time 1 hour 45 minutes
2 tablespoons unsalted butter, softened, plus more for dish
1 cup heavy cream
1/2 cup low-sodium chicken broth
1 1/2 ounces (1 cup) fresh morel mushrooms, washed, patted dry, and halved or quartered if large
1 stem green garlic, trimmed and cut into 1/4-inch slices (or 2 small cloves fresh garlic, sliced)
1 1/2 pounds white all-purpose or Yukon Gold potatoes (3 medium)
2 medium leeks (white and pale-green parts only), cut on the diagonal into 1/2-inch slices and rinsed well
Zest of half a lemon
Preheat oven to 375 degrees. Generously butter a 2 1/2-quart baking dish. Bring cream, broth, morels, and green garlic to a simmer.
Assemble the gratin: Peel potatoes, and cut crosswise into slices slightly thicker than 1/8 inch. Layer potatoes in dish, overlapping slightly. Spread half the leeks over top, and season with salt. Pour half the cream mixture over top. Repeat.
Cover gratin with foil, and bake 40 minutes. Uncover, and bake until potatoes are tender and golden and most of the liquid is absorbed, 20 to 25 minutes more. Let cool 15 minutes. Before serving, sprinkle with lemon zest.