• 2 Tbs. unsalted butter
• 4 c. thinly sliced onions
• 1 ¼ lb. butternut squash
• 1 ¼ lb. Yukon Gold potatoes
• 1 c. half-and-half
• 1 tsp. salt
• ½ tsp. black pepper
• 2 c. fresh sourdough breadcrumbs
• 2c. grated gruyere cheese
• 1 ½ Tbsp. fresh sage

Peel seed and slice squash into ¼-inch thick slices. Peel and cut potatoes into ¼-inch thick slices. Preheat oven to 350 degrees. Butter a 13-by-9-inch baking dish. Melt butter in a large, heavy skillet and add onions. Cook over medium-high heat until deeply caramelized, 20 to 30 minutes. Lay alternate layers of squash and potatoes in baking dish. Layer onions on top. Mix half-and-half, salt and pepper and pour over onions. Cover tightly with foil and bake 90 minutes. Increase oven temperature to 400 degrees. Mix breadcrumbs, cheese and sage in medium bowl. Sprinkle over gratin. Bake uncovered until top is golden brown and crisp, about 30 minutes.

Serves 8.