Brigit Binns' Crab Cakes

INGREDIENTS

• 1 1/4 cup (5 oz/155 g) fine dried bread crumbs
• 1 1/2 tablespoon Dijon mustard
• 1 tablespoon water, if needed
• 3 tablespoons unsalted butter
• 1 cup (8 fl oz/250 ml) heavy (double) cream
• 1 egg, lightly beaten
• 1 pound (500 g) lump crabmeat
• 1 1/2 tablespoon finely chopped jarred pimiento (sweet pepper)
• 2 tablespoons vegetable oil
• Salt and freshly ground white pepper
• 1/2 lemon, cut in wedges, for serving
• 2 tablespoons finely chopped yellow onion
• 2 celery stalks, finely chopped