Brie cakes with sun-dried tomatoes

1½ cups water;
¾ cup steel-cut oats.
CAKES:
2 ounces firm Brie, cut into ¼-inch cubes (about ½ cup);
1½ cups quick-cooking oats (not old-fashioned rolled oats);
½ cup finely chopped red onion (about ½ onion);
⅓ cup well-drained and chopped oil-packed sun-dried tomatoes;
⅓ cup toasted pine nuts;
2 large eggs, lightly beaten;
1 tablespoon minced fresh rosemary, or 1 teaspoon dried;
1 tablespoon minced fresh sage, or 1 teaspoon dried;
1 to 2 teaspoons minced fresh red Thai chile (optional);
½ teaspoon fine sea salt;
¼ teaspoon freshly ground black pepper.
YOGURT-KETCHUP SAUCE, AND TO FINISH:
1 cup plain whole-milk yogurt;
2 tablespoons ketchup;
½ hot red chile, cut into small rings, or 1 teaspoon Asian chile sauce such as sriracha;
Fine sea salt;
2 tablespoons extra-virgin olive oil.

To prepare the oats, bring the water and oats to a boil in a 2-quart saucepan. Cook, uncovered, for 2 minutes over medium to medium-low heat, stirring a few times. Remove from the heat, cover, and let sit at room temperature until the liquid is absorbed, about 1 hour. Transfer the oats to a large bowl and spread to cool for about 10 minutes.
To make the cakes, add the Brie and all the remaining ingredients to the bowl with the oats. Using your hands, thoroughly combine the mixture until the ingredients come together.
Level the mixture inside the bowl and divide it into 8 equal portions using a butter knife (cut in half like a cake, and then each half into quarters). Moisten your hands with water and form cakes about 3 inches in diameter. Place the cakes on a small baking sheet or large plate.
To make the sauce, combine the yogurt, ketchup, and red chile in a small bowl. Season with salt to taste.
To finish, heat 1 tablespoon of the olive oil in a large skillet over medium heat until it shimmers. Add 4 cakes and cook 4 to 5 minutes on each side or until golden brown, carefully turning once with a metal spatula. Add the remaining 1 tablespoon olive oil and repeat with the second batch. Serve warm or at room temperature, together with the yogurt-ketchup sauce.
TO GET A HEAD START: Make the oats, as in step 1, ahead. The cakes, up through step 3, can be prepared 6 hours ahead. Chill, covered.
TO LIGHTEN IT UP: Bake the burgers instead of pan-frying.