Sauté shallots in butter in a saucepan over medium heat for 5 minutes or until soft, add peas and stock and simmer for 5 minutes or until tender and stock has almost reduced. Season to taste with sea salt and freshly ground black pepper, set aside and keep warm.
For hollandaise, combine vinegar, wine, shallots and peppercorns in a small saucepan, simmer over medium heat and reduce by half, then strain into a large heatproof bowl. Add egg yolks and whisk over a saucepan of gently simmering water until pale and frothy and thick enough to hold a ribbon when drizzled from the whisk. Remove from heat, gradually whisk in butter and season to taste.
Serve fish with peas and hollandaise.
Note For clarified butter, melt 250gm cold cubed butter over
low heat for 10 minutes, pour into a jug, stand, skim surface, then
pour off clear butter and reserve, discarding milk fat.