Firstly, take a bowl and place a sieve over it. Put a muslin cloth and add 1 cup curd to it.
Put some weight till all the extra water is drained out.
After a few hours, the hung curd is ready. Transfer it to a bowl.
Also, add ½ chopped onion, 1 tsp chopped green chilli, 1 tbsp chopped coriander, ½ tsp salt, ½ tsp oregano, and give it a good mix.
Further, take 4 brown bread slices.
Now, take a slice, spread the prepared mixture over it, and cover it with another bread slice. Similarly, prepare the other slices.
For tadka, heat a tawa & add 1 tbsp oil, 1 tsp mustard seeds, and 8 curry leaves.
Keeping the flame at the medium, place the bread sandwich over it. Roast it until golden brown and crispy.
Apply oil on top and flip it. Roast it from the other side too.
After being perfectly cooked on both sides, remove it from the tawa. Similarly, roast the other sandwich.
Cut it from the centre and divide the sandwich into two equal parts.
Finally, enjoy dahi tadka sandwich with green chutney and tomato ketchup.