Mix the butter with the garlic, thyme and lemon zest and shape into one fat sausage shape then wrap in greaseproof paper and refrigerate or freeze until solid.
Mix the breadcrumbs with the hazelnuts and put to one side.
Make a horizontal slash deep into the fattest part of the chicken breast, at least 2cm deep and at least 4 – 5 cm long to create a cavity in which to stuff the butter. Put the prepared chicken breast between two sheets of greaseproof paper then using a rolling pin, bash the chicken breast to flatten and broaden the shape a bit, about ¼ more in size. This will help the chicken when breadcrumbed to cook more evenly.
Cut the cold butter into 4 lengths and place each piece into the prepared cavity of the chicken breast. Seal the chicken around the butter as best you can, leaving no butter exposed.
Have 3 wide bowls or plates ready, one with the flour, one with the egg and one with the mix of breadcrumbs and hazelnuts. Dust each chicken breast with the flour, then dip into the egg and finally smother with the breadcrumb mix. Place the finished chicken breasts on a plate. Make sure all of the chicken is coated with the mixture as this will help prevent any of the flavoured butter from leaking out during the cook time, though some inevitably will.
Put the chicken in the fridge for an hour, or more, to thoroughly chill the butter once again before you cook the chicken.
When ready to cook preheat the oven to 180C.
In a good-sized frying pan over a moderate heat, add the oil and a good-sized knob butter, when the fat in the pan is hot, brown the chicken breasts for 2 - 3 minutes on each side until crisp and golden, add a good-sized knob more of butter to the pan just at the end of the cook time.
Place the browned chicken breasts on a baking tray in the oven and cook for around 20 mins, until the chicken is cooked through. If using a digital thermometer, the internal temperature of the chicken breast should read 75°C.
Remove from the oven and serve the chicken with the lemon wedges on the side and some cooked green beans.
You can watch Claire make this recipe over on her Instagram channel here.
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