In a pre heated pan, add a little olive oil. Add the shallots and garlic and cook for 1 minute, then add the white wine and the vinegar.
Reduce the mixture by half, then add the chicken, mushrooms and cream. Cook for a further 3 to 4 minutes.
Add the broccoli and onions, season, then add the chopped tarragon.
Once at the desired consistency, cut out the centre of the puff pastry case, leaving a 1cm gap around the edge, fill with the chicken filling and serve.