Sweet Potato Au Gratin with Caramelized Onions

Ingredients

4 tablespoons butter, divided

2 large, sweet onions cut into thin slices

2 sweet potatoes, peeled and cut into thin slices

2 tablespoons flour

Pinch of cayenne

1 tablespoon fresh sage, minced plus more for garnish

1 tablespoon fresh rosemary, minced plus more for garnish

2 cups milk

1 ½ cups gruyere cheese, shredded and divided

Salt and pepper to taste

Preheat oven to 350 degrees.

Directions

Melt 2 tablespoons butter in a large skillet add onions and cook for 5 minutes at medium high heat, stirring frequently.  Reduce heat to low.  Continue to cook stirring occasionally until onions cook down and caramelize approximately 30 minutes. While cooking if the pan becomes dry, add water 1 to 2 tablespoons at a time to prevent onions from burning and to encourage caramelization.  Set aside.

In a saucepan melt remaining 2 tablespoons butter.  When butter is melted, stir in flour, and stir constantly over medium heat for 2 to 3 minutes or until flour begins to smell fragrant and a bit nutty.

Whisk in milk, sage, rosemary, and a pinch of cayenne until smooth.  Cook stirring frequently until bubbles begin to form on the surface then cook 2 minutes more.  Remove from heat and stir in 1 cup cheese until cheese is melted and well combined.

In a buttered casserole dish alternate layers of sweet potatoes, then caramelized onions until all are used up (starting with and ending with sweet potatoes).  Salt and pepper in between layers.

Pour cheese sauce over the top.

Bake covered for 45 minutes.  Remove the cover, top with the remaining cheese, then bake another 15 minutes or until the top is golden brown.

Let stand at least 15 minutes before serving.

Garnish with rosemary and sage.