Put the raisins and verjuice in a bowl and microwave
on defrost setting (or warm gently in a pan) for 5 minutes,
then cool. Strain, reserving both raisins and verjuice.
Strip the rosemary leaves from the stalks and reserve
the leaves for another use. Put the stalks into a bowl with
3 tbsp olive oil and a little freshly ground black pepper.
Add the chicken breasts and marinate for at least 1 hour.
Choose a wide frying pan with enough room for the
chicken breasts to cook with lots of space between them.
Toss the pine nuts with a little olive oil over medium heat
in this pan until golden brown, then cool on a paper towel.
Heat the butter in the pan until golden brown, then add
1 tbsp olive oil to stop it burning. Pan-fry the chicken, skin
side down, over moderate heat until golden, 6-10 minutes.
Turn and cook the other side for 3-4 minutes. (The total
cooking time depends on the thickness of the meat, but
two-thirds of the cooking time should be on the skin side.)
When the chicken is cooked, season, remove from the
pan, then rest, skin-side down. Discard any butter from pan
and toss in the raisins. Pour in the reserved verjuice and
deglaze the pan over the heat until the liquid has reduced
by half. Stir in the pine nuts and return the chicken to
the pan. Taste the sauce for seasoning before serving.