Pre heat your oven to 180°c.
In the thickest part of each chicken breast, using a knife, slice a small incision and push the knife through to make a tunnel, try not to go all the way through. Push each cheddar piece into the chicken, like a pipe cleaner inside a pipe.
Then gently fold the prosciutto round each breast until tightly sealed.
Place inside foil, seal and bake for 25 minutes, then open up the foil and let the prosciutto brown for a further 15 minutes or until cooked through (75°c or over).
Meanwhile
Add the butter to a small saucepan, heat until clarified and then add the flour, mix to a paste then add the milk and whisk as you go, add the mustard, some pepper if desired and then add the cheese, bring to the boil and simmer until smooth and thick.
Add slightly steamed broccoli and simmer for a minute before serving.
Remove the chicken from the foil and slice into 3 pieces, place on top of the sauce.
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