Add the chicken to a small sauce pan. Remove one or two outer layers of the lemongrass and cut off the top and bottom. Cut into 2 inch pieces and add them to the pan. Add in the lime leaves

Pour in the broth with a pinch of salt and pepper. Bring to a simmer and cook uncovered, flipping the chicken occasionally, until it is cooked through and the broth has reduced a bit. About 20 minutes.

Pour the broth and chicken into a bowl and cover. Set in the fridge to cool for at least 1 hour.

Put some olive oil into a large frying pan over high heat. Add the mushrooms and cook about 10 minutes, stirring often, until browned and reduced in size. Let cool for 5 minutes while you cut the chicken.

Remove the chicken from the broth and cut against the grain into small ½ inch pieces. Add to a large bowl.

Add in the mushrooms and all the remaining chicken salad ingredients. Add in ¼ cup of the broth that the chicken was cooked in. (Do not add the lemongrass or lime leaf from the broth)

Stir well to combine. Allow to cool in the fridge for 1 hour before serving.

Warm the bread under the broiler on all sides to soften. Slice open, leaving the hinge. Spread the insides very lightly with mayo.

Add cheese, then line with the tomato and cucumber slices. Add on the chicken salad, and top with some cilantro.

Wrap with parchment to help with sandwich integrity, or serve immediately!