For the parsley oil, blend the garlic, parsley and walnuts as finely as possible in a food processor, then gradually add the oil in a thin stream, blending continuously, until smooth and well combined. Season, to taste, with salt. Set aside until needed.
For the stuffed tomatoes, in a large bowl, mix together the flaked salmon, smoked salmon, mayonnaise, garlic, ketchup and balsamic vinegar until well combined. Season, to taste, with salt and freshly ground black pepper.
Stuff the tomato halves with the filling mixture. Set aside.
For the green bean and shallot salad, blanch the beans in a large pan of salted, boiling water for 1-2 minutes. Drain well and run under a cold tap to refresh.
In a bowl, whisk together the oil, vinegar and mustard until well combined. Add the blanched beans and the shallot rings and stir to coat them in the dressing. Season, to taste, with salt and freshly ground black pepper.
To serve, place two stuffed tomato halves, cut sides facing downwards, onto each of four serving plates. Drizzle over the parsley oil. Spoon the salad alongside.