This is a Rhona special created for me because I love cheese and onion so much. When sandwiches are good they are great.

Ingredients
½ onion, very finely chopped
125g cheese, finely grated 
2 tbsps mayo 
1 tsp milk 
Freshly ground pepper 
Salt to taste 
4 slices of bread (I really like M&S oaty or granary with this) 
Butter 

Method
Mix the onion, cheese, mayo and milk and season to taste. 

Butter the bread, spread your cheese and onion mix over 2 slices of bread.  Put the tops on the sandwiches and cut into 4.