Out of all my mom’s greatest breakfast hits, dahi toast is easily the most the beloved in our family. This sandwich—a loose interpretation of a recipe from one of my dad’s friends—is totally unexpected (who would ever think to put yogurt between bread?!) and impossible not to like. Imagine a tangier, spicier grilled cheese sandwich. You get that satisfying oily bread crunch, but with onions, chiles, and (my favorite part) a crispy topping of black mustard seeds and curry leaves added into the mix. The glue that holds this recipe together is the tang of the sourdough bread—it’s the perfect foil to the rich, ricotta-like filling. We are a house divided when it comes to accompaniments for dahi toast—my mom and sister like cilantro chutney, while I prefer ketchup. My dad uses both: He swirls the chutney and ketchup together to create a kinda ugly-colored but admittedly delicious super-sauce.
In a butter warmer or small pan over low heat, warm the oil. Once the oil is warm but not super hot, add the black mustard seeds and as soon as they begin to pop and dance around in the oil, which should be within seconds, remove the pan from the heat. Add the curry leaves, making sure they get fully coated in the oil (there may be more popping and splattering, and that’s okay!). The leaves should immediately crisp up in the residual heat. Set aside.
In a small bowl, mix together the yogurt, onion, cilantro, green chiles, salt, black pepper, and red chile powder. Spread the yogurt mixture over 6 slices of the bread and top with the remaining slices to make 6 sandwiches.
In a large pan over medium heat, warm 1 teaspoon oil. Once the oil begins to shimmer, reduce the heat to low and add as many sandwiches as will fit in the pan. Cook until the undersides are crisp and lightly browned, 3 to 4 minutes, then flip them, add another teaspoon of oil to the pan, and cook until the other side is crisp and slightly browned, 3 to 4 minutes more. Transfer the sandwiches to a platter and repeat to cook the remaining sandwiches.
Divide the spiced oil mixture evenly over the top of the sandwiches. Cut each sandwich in half and serve immediately with a side of ketchup and/or chutney, if desired.