The tongue would have to be one of the most underrated cuts of
beef. Don't tell squeamish guests what you're serving; they'll
never guess. The raspy exterior peels away easily once the tongue
Cover tongue in a saucepan with plenty of cold water, bring to the boil over medium-high heat, then reduce heat to medium and simmer for 2 hours or until tender. Drain then, when cool enough to handle, peel off skin and thinly slice tongue across the grain.
Meanwhile, for sauce gribiche, process boiled and raw egg yolks in a food processor with vinegar and mustard until combined then, with motor running, add oil in a thin steady stream until emulsified. Season to taste with sea salt and freshly ground white pepper. Finely chop cooked eggwhite and add to sauce with remaining ingredients, stir to combine and refrigerate until required.
Split baguette lengthways and spread generously with butter. Spread with sauce gribiche, then layer on tongue, radish, celery and sliced boiled egg, cut into portions and serve.