Prepare the Slurry: In a wide mixing bowl, add 4 tablespoons of besan, turmeric powder, red chili powder, ajwain, and salt. Mix the dry ingredients well.
Make the Batter: Gradually add water and whisk into a smooth, lump-free batter. The consistency should be thin and pourable (similar to an egg omelet mixture).
Add Veggies: Fold in the finely chopped onions, tomatoes, green chilies, and fresh coriander leaves into the batter. Mix thoroughly.
Heat the Tawa: Heat a non-stick tawa or skillet over medium heat. Brush it lightly with half a teaspoon of oil or ghee.
Dip and Place: Take one slice of whole wheat bread, dip it quickly into the besan batter on both sides so it coats evenly (do not soak it for too long, or the bread will break). Place it immediately onto the hot tawa. Spoon some extra veggies from the bowl onto the top of the bread.
Toast to Perfection: Cook on medium-low heat for 2–3 minutes until the base turns golden-brown and crispy. Flip the toast, apply the remaining oil around the edges, and cook the other side for another 2 minutes until the raw smell of besan is completely gone.
Serve: Repeat the process for the second slice. Cut diagonally and serve hot with fresh mint-coriander chutney.