a skillet over medium or medium-high heat, melt
2 tablespoons of the butter. Add scallops and
sauté stirring constantly, until cooked
through, about 5 minutes. Remove with a slotted
spoon to a serving dish and keep warm.
pan to medium heat and add remaining 2 tablespoons
butter, mushrooms, onions, and garlic. Cook,
stirring, about 3 minutes. Add wine, raise heat
to medium-high, and boil until liquid is reduced
to about 2 tablespoons, about 2 minutes. Reduce
heat to medium, add half and half, and cook,
stirring occasionally, until slightly thickened,
about 3 mintues. Stir in mustard, lemon juice,
salt, and pepper and mix well.
scallops to pan and reheat to serving temperature.
Transfer to a warmed serving dish, sprinkle
with parsley and serve immediately.