Method:
Heat butter and a splash of olive oil in a shallow pan on a high heat until bubbling.

Throw in onions and garlic and saute until golden brown.

Throw in lamb fillets and rosemary and sear until done (5-8 minutes).

Meanwhile, prepare 200ml chicken stock, and throw into a pan on a high heat. Add 2 teaspoons of dijon mustard (to taste), a splash of white whine (or other alcohol - cointreau?) and the apply, finely chopped or grated. Add salt and pepper.

Reduce heat and stir until fused but without boiling. At the last moment, add cream (bit by bit) and stir in, until the sauce combines and thickens. Should be about 1/3 of the cream, but use taste as your guide. The sauce will have lumps of apple in it. This is fine.

Serve fillets of lamb on a bed of rocket and watercress salad, topped with sauce. Goes very nicely with a crisp Pinot Grigio.