Start by making the garlic butter. Mix the butter, garlic, parsley and lemon juice in a bowl and season with salt and pepper. Portion the butter into two flat, thin pieces, approximately 2 cm wide and 4 cm long, so that they’ll slot into the opening in the chicken breast. Wrap in foil and put in the fridge to harden while you prepare the chicken.
Cut the ‘false fillet’ off the chicken breasts (the small piece of muscle on the side) and keep to one side as you’re going to use these to plug the hole in the side. Lay each breast flat, push down on the top to level it flat and carefully slice through the middle, front to back, so that there’s a cut down one side. Don’t cut all the way through; the cut needs to go about three quarters of the way through.
Take the garlic butter from the fridge and place a piece inside each breast. Take the false fillets and slot them in after the garlic butter to help ‘plug’ the cut on each breast.
Mix the tarragon with the flour. Roll each stuffed breast in the seasoned flour, then dip in the egg and finally cover really well with breadcrumbs. Wrap in foil and place in the fridge for 30 minutes.
Take the kievs out of the fridge and repeat the coating process: flour first, then egg and then breadcrumbs.
Preheat the oil in a deep fat fryer or large heavy-based saucepan until a cube of bread browns in 20 seconds. Carefully lower the kievs into the hot oil and fry for 20 minutes, or until cooked through, turning carefully once halfway through cooking.
Remove with a slotted spoon and drain the excess oil on kitchen paper, then serve the kievs with a lemon wedge to squeeze over the top, buttery crushed potatoes and salad leaves, if you like.
You can also make chicken cordon bleu using the same technique; simply substitute garlic butter for a slice of emmental cheese rolled up in a piece of British ham!