3 tablespoons extra-virgin olive oil
1 medium white or yellow onion, chopped
3 cloves garlic, chopped
2 1/2 to 3 cups sweet potatoes, peeled and diced into 1/4-inch pieces
1/2 teaspoon salt (plus more to taste)
1 tablespoon adobo sauce from a can of chipotle chilies (or more to taste)
1 cup corn kernels, fresh or frozen
2 cups cold whole or low-fat milk
2 tablespoons cornstarch
1 box puff pastry dough (allow 20 to 30 minutes to thaw)
1 egg white