Potato and Squash Gratin

http://www.thekitchn.com/recipe-potato-squash-and-goat-90647

This was good, but turned out really watery and undercooked when I followed the directions.  Maybe I had too much summer squash or maybe it's because we only had 2% milk.
So I'm going to try adding a few Tbs of flour to the layers and cook it for longer next time (maybe 75-80 minutes total?)
But it was good, and a great way to use up summer squash/zucchini

2 medium yellow squash
4 small to medium red potatoes
3 tablespoons olive oil
4 ounces goat cheese
salt and pepper (a sprinkle of dried thyme or chopped chives is also good)
1/4 cup milk
1/3 cup freshly grated parmesan cheese
1 tablespoon thinly sliced basil, optional

Preheat oven to 400°F.

Use a mandoline or chef's knife to slice the squash and potatoes into very, very thin slices, 1/8-inch or less. Toss the sliced vegetables with the olive oil in a large bowl.

Pour a small drizzle of olive oil in a casserole dish (around 8 or 9 inches square) and spread it around the bottom and sides. Place 1/3 of the squash and potato slices in the bottom of the dish—no need to layer them squash-potato-squash-etc.—then season with salt and pepper. Top with half of the goat cheese, scattered evenly in large chunks. Repeat with another 1/3 of the vegetables, seasoning again with salt and pepper and topping with the other 1/2 of the goat cheese. Finish by layering on the final 1/3 of the vegetables and seasoning with salt and pepper.

Pour the milk over the entire dish. Top with the parmesan cheese. Bake, covered, for 30 minutes, then uncover and bake 15 more minutes, until the top browns. Scatter on the fresh basil, if using.