Dahi Toast

Name: Dahi Toast
Ingredients: 1/4 cup extra-virgin olive oil, plus more for cooking the toasts; 1 1/2 teaspoons black mustard seeds; 3 sprigs fresh curry leaves, stripped (24 to 30 leaves); 1 cup low-fat plain Greek yogurt; 1/2 medium red onion, finely diced; 1/2 cup finely chopped fresh cilantro (stems and leaves); 2 small Indian green chiles or serrano chiles, finely chopped; 1 teaspoon kosher salt, plus more to taste; 1/2 teaspoon freshly ground black pepper, plus more to tste; 1 pinch red chile powder (like cayenne), plus more to taste; 12 large slices white sourdough bread; Ketchup, for serving (optional); Cilantro chutney, for serving (optional)