Mix the tomato sauce with the softened butter, loose thyme leaves, capers and olives. Divide into eight equal parts and allow to set in the freezer for about 30 minutes.
Pour the flour and breadcrumbs into two different dishes. In a bowl, beat the eggs with a pinch of salt and pepper.
Divide the chicken breasts in half before quartering them to make eight pieces. Form a pocket in each piece, cutting only on one side.Fill the pockets with the tomato sauce, ensuring it is well squeezed in.
Brush the edges of the cuts with a little beaten egg. Coat the stuffed chicken pieces firstly in the flour, then the egg and finally the breadcrumbs. Repeat the process to obtain two layers of breadcrumbs.
Heat the oil in a high-sided pan to a temperature of 160°. Fry the chicken pieces for about 6/8 minutes or until golden brown.