In a frying pan over a medium heat, warm a little oil and add the bacon. Fry for 5 to 7 minutes on each side until brown and no longer pink in the centre. Remove from the pan and halve each slice. Set aside.
To make four sandwiches, lay the bread out in pairs in front of you then spread with mayonnaise and mustard. Divide the remaining ingredients between four slices of bread, including the bacon, then place the second piece of bread on top. Slice and serve immediately.
This recipe will work for any type of sliced bread including sourdough. Feel free to toast the bread before creating the sandwich.