Bring a large pot of salted water to a boil, carefully place lobster tails in the pot and cook about 1 minute per ounce. If the average weight of the tails is 4 ounces it will take about 4-5 min total. Remove from the pot and allow to cool before removing the shells with kitchen shears. To remove: cut along the length of the tail and pop out the meat. Reserve shells. Chop lobster meat into bite size pieces and set aside.
Heat the chicken stock and reserved lobster shells in a small pot over medium high heat, bring to a boil, reduce heat to low and simmer for 20 minutes. Remove shells and keep stock over low heat
In a large sauté pan over medium high heat melt the butter and cook the leeks until soft about 5 min.
Add the arborio rice to the leeks and butter and cook the rice for 3 min.
Add the white wine and a big pinch of saffron, stirring often and cook until the wine is almost gone.
Start adding the stock 1/2 cup at a time, making sure not to add more until the previous addition has been absorbed, stirring often.
Once the rice is just tender add in the parmesan, lobster pieces and frozen peas. Continue stirring to melt cheese and warm the lobster.
Remove from the heat, season with salt and pepper and serve with additional parmesan, chopped chives and a squeeze of fresh lemon