- Boil potato on a pot
 - After the potato is boiled properly, take it on a pot and smashed it properly
 - Cut onions, capsicum, carrot, green chilli and start to fry it
 - Add salt [and sugar]
 - Once the vegetables start to turn brown, add smashed potato on it and smashed some more and mix the potato with the vegetable.
 - Toast two pieces of bread
 - Put the smashed potato with vegetable inside the two breads
 
Very easy. And your smashed potato sandwich is ready to serve.