Pound sage, thyme, garlic, and olive oil into a thick paste using a mortar.
Smear the herb paste over the lamb fillets.
Simmer beans, red onion, garlic, thyme, tomatoes, and parsley in oil for 4 minutes.
Add balsamic vinegar and lemon juice to the beans and season well.
Sauté sliced leeks in olive oil until softened.
Add balsamic vinegar and brown sugar to leeks and cook for 5 minutes.
Sear lamb fillets in a hot frying pan for 2 minutes per side.
Deglaze the lamb pan with a splash of balsamic vinegar and stir into the chutney.
Serve lamb fillets over the bean mixture and drizzle with the hot chutney.