Sauté the shallot cubes and garlic in butter, add fish stock, Noilly Prat and whipping cream and boil to half.
Whisk the butter into the sauce with a hand mixer.
Clean and rinse the spring onions and cut into fine rings. Add to the sauce form and pull a tiny bit (the scallions should still be al dente). Season with salt and pepper and fold in the chopped tarragon and diced tomatoes just before serving.
Serving example: with salmon in puff pastry (see sep. recipe).
Distribute the spring onion ragout evenly on plates, cut the fried salmon into pieces and arrange on top.