BRING A LARGE POT OF SALTED WATER TO A BOIL.
MEANWHILE, TRIM THE STEMS FROM THE STRING BEANS.
FILL YOUR SINK WITH COLD WATER.
BOIL THE BEANS FOR 3 TO 5 MINUTES, TESTING FREQUENTLY. THEY SHOULD BE TENDER BUT STILL CRUNCHY. DRAIN AND DUMP INTO THE SINK WITH THE COLD WATER. ONCE THEY'VE COOLED, DRAIN IN A COLANDER THEN ARRANGE ON A KITCHEN TOWEL. ROLL GENTLY AND RESERVE.
IN THE BOTTOM OF YOUR SALAD BOWL SCATTER A HEALTHY PINCH OF SEA SALT AND SEVERAL GRINDINGS OF BLACK PEPPER. ADD 2 TBSPS OF CHAMPAGNE VINEGAR AND 1 TBSP OF BANYULS OR SHERRY VINEGAR. PEEL AND FINELY DICE THE SHALLOT. STIR INTO THE BOWL. WHISK TOGETHER WITH 1 TBSP OF GRAINY MUSTARD. WHISK IN 2 TBSPS OF HAZELNUT OIL AND 4 TBSPS OF OLIVE OIL.
USING THE TRAY IN A TOASTER OVEN OR A RIMMED BAKING SHEET IN THE OVEN, TOAST THE HAZELNUTS FOR 5-8 MINUTES AT 325ยบ. THEY SHOULD BE LIGHTLY BROWNED. WHEN THE HAZELNUTS HAVE COOLED, CHOP THEM ROUGHLY. (IF YOU USE A KNIFE WITH A CURVED BLADE OR A MEZZALUNA THE NUTS WON'T ROLL ALL OVER THE PLACE.)
JUST BEFORE SERVING TOSS THE BEANS WITH THE DRESSING. ADD CHOPPED HERBS AND SCATTER THE HAZELNUTS ON TOP.
SERVES 4-6 EITHER AS A FIRST COURSE OR A SIDE SALAD.