Potato Gratin

Every fall, I like to make this dish:
1.5 lbs. red potatoes cut into 1/8'' thick slices
1 cup red onion sliced thin
3 TBS. chopped fresh basil
1/2 cup veggie broth
2 tsp. oil
1/2 grated asiago cheese
salt and pepper

Preheat oven to 400 degrees. Coat 8x8'' baking dish with cooking spray (or a little oil). Arrange 1/3 of the potato slices in the bottom of the pan. Top with 1/3 of the onion slices, 1 TBS. of the basil, 1/4 tsp. salt, 1/4 tsp. pepper. Repeat the layers again twice, using everything but the oil and broth.
Drizzle oil and broth over the potatoes. Cover, and bake for 40 minutes. Uncover, and back for 25 minutes more.
Sprinkle the potatoes with the grated asiago cheese and back another 5 minutes or so until the cheese browns.