Firstly, In a mixing bowl, add mayonnaise, veggies, and seasonings. Mix everything well.
Cut the brown edges of the bread (optional).
Apply some butter to both slices of the bread.
Spread veg-mayo mixture generously on one slice of the bread slice.
Finally, Cover and press with another bread slice over it, and cut them into triangles/squares.
Serve Eggless Veg Mayonnaise Sandwich with ketchup.
Notes
Tips to Make the Best Mayonnaise Sandwich
Toast the bread: You may toast the bread on Tawa or use a sandwich maker or grill it to golden brown and crisp. This will give a nice crunch and prevents the sandwich from getting soggy from the mayonnaise and veggies.
Butter: Smearing butter on the bread acts as a moisture barrier, i.e., slows down the transfer of moisture from the filling to the bread, hence preventing the bread from getting soggy. So don't skip it.
Variations
Bread: Use any bread of your choice, like brown, multigrain bread, or white.
OtherVeggies: You can add other vegetables of your choice, like regular or spring onion, sweet corn kernels, lettuce, cucumber, tomatoes, and celery.
Cheese: If you like it cheesy, add shredded cheese like mozzarella, cheddar, or cheese slice in between, and then toast the veg mayo sandwich if you like.
Vegan: use vegan mayonnaise and butter.
AddProtein: You can also add mashed chickpeas, crumbled paneer, or tofu to make it nutritious.
Note: Nutrition values are my best estimates. If you rely on them for your diet, use your preferred nutrition calculator.