Combine the salad leaves with the herbs in a bowl. Add the walnut oil and 1 teaspoon of the olive oil and toss well. Arrange on a serving platter or plates.
Peel the celeriac and cut it into match-sticks. Toss with the lemon juice. Core the nashi pear and cut it into similar-sized strips. Toss with the celeriac and lemon juice, then scatter the celeriac and pear over the salad leaves.
Heat the remaining olive oil in a large frying pan. Add the shallots and cook, stirring from time to time, for 4–5 minutes or until lightly browned. Add the cabbage and toss for 1 minute, then pour in the vinegar and boil until the vinegar has reduced by about half. Add pepper to taste and remove from the heat.
Add the green and red grapes and walnuts to the hot cabbage salad. Spoon the cabbage salad and its juices over the dressed leaves, celeriac and pear, then serve immediately.