Shrimp Scampi

This is an okay dish that takes close to no time to make. I've had better shrimp scampi but they take much longer to make than this. Since I don't have that much time during the day, this one will do when I crave for some shrimp Scampi.

2 pounds shrimp, peeled and deveined - tails left on
Salt and freshly ground black pepper
Olive oil
1 small onion, sliced thinly
2 tablespoons chopped garlic
1 lemon, juiced
1/2 cup white wine
1/2 cup shrimp stock, recipe follows
2 tablespoons cold butter
2 tablespoons chopped parsley leaves
Lemon slices, for garnish
Rice, as accompanimentSeason the shrimp thoroughly with salt and pepper. Heat a large saute pan over medium-high heat. When the pan is hot, add enough oil to lightly coat the pan. Add the shrimp and quickly saute until just starting to turn pink, but not cooked through. Remove from the pan and set aside. Add the onions and saute just until they begin to soften, about 3 minutes. Add the garlic and cook another 30 seconds. Add the lemon juice, white wine, and stock, and reduce by 2/3, about 5 minutes. Add the shrimp back to the pan and swirl in the butter. Finish with the parsley and check for seasoning. Garnish with lemon slices and serve over rice.