In a pan on medium heat, add 1 tablespoon butter
Once heated, add broccoli and onion, cooked until broccoli is tender and onion is translucent, then add garlic, cooking for 30-60 seconds.
Butter the outside of each slice of bread
Top bottom slice with 1/4 cup shredded cheddar cheese, broccoli & onion mixture, chicken meat, another 1/4 cup of shredded cheddar cheese, and your remaining slice of bread.
Fry in a non-stick pan on medium-low heat until bread is golden brown and cheese is melted.