Preheat the oven to 220ºC/200ºC Fan
Add the butter to a small (around 20cm) oven proof dish and sweat the leeks in the butter until soft
Add the chicken thigh and plain flour and cook for a couple of minutes until just sealed
Add in the tarragon, mustard, creme fraiche, spinach, water and chicken stock
Stir and cook down for 4-5 minutes until the spinach has wilted and the sauce has thickened slightly
Add pepper and a pinch of salt
Toss the gnocchi in the parmesan, garlic and salt then scatter over the top of the chicken filling
Bake for 15 minutes
Turn the grill on to max and cook for 10-15 minutes until the gnocchi is crispy
