I have to get this recipe down before I forget how I made it. I wanted to make a savory galette like I did recently with cabbage and sausage (only this time I stir-fried the cabbage, red onion, and garlic before baking it and I think that was better), but with sweet potatoes. I couldn't really find a suitable sweet potato filling so I made this one up that turned out to be really, really good.
I used a half recipe of the pastry I always make (1.5 cups whole wheat flour, 1/2 tsp salt, 1/2 cup grated cold butter, 2 tablespoons lemon juice, and a bit of water). I had too much filling, but I was trying to so I'd have plenty and could use it for leftovers too.
Prick 3 large sweet potatoes and cook them in the oven or microwave till they're nearly done. Let them cool, then peel and chop into bite-sized pieces.
While the sweet potatoes are cooking, chop one large onion and a tart apple like a Granny Smith. Sauté the onion till soft, then add the apple and cook till the apple has softened but still holds its shape well. Add the sweet potatoes, salt and cayenne to taste, and Old Bay seasoning (I think I put in about a teaspoon) and cook for a few more minutes till everything is hot and flavorful and as soft as you want it to be.
Roll out the pastry and put it on a cookie sheet. Mound the filling into the middle, leaving about 1.5 inches around the edges, then fold the edges up to make a rim around the vegetables. There will be a large hole at the top.
Bake at 350 for about 30-40 minutes. Let it sit a few minutes before serving.
The tart apples were perfect with the sweet potatoes. You could use different seasonings if you like.