Bring a medium saucepan of salted water to a boil over medium-high heat. Add the lobster tails and boil for 8 to 10 minutes until the shells curl and the lobster meat turns white. Drain, transfer to a cutting board, and cool for 15 minutes. Using kitchen shears or a sharp knife, cut through the top shell lengthwise. Remove the meat and cut into 1/2-inch pieces. Set aside.
In a medium saucepan, bring the chicken stock to a boil. Keep hot over low heat.
In a large saucepan, melt 3 tablespoons of butter over medium heat. Cook until the butter begins to foam and then turns brown, about 1 to 1 1/2 minutes. Add the onion and cook, about 3 minutes. Add the rice and stir to coat with the butter. Add the brandy and simmer until the liquid has almost evaporated, about 3 minutes. Add 1/2 cup of stock and stir until almost completely absorbed, about 2 minutes. Continue adding the stock, 1/2 cup at a time, stirring constantly and allowing each addition of stock to absorb before adding the next. Cook until the rice is tender but still firm to the bite, about 20 minutes. Remove from the heat. Stir in the Parmesan cheese, the remaining butter and 2 tablespoons chives. Season with salt and pepper, to taste.
Transfer the risotto to a large serving bowl. Arrange the lobster meat on top of the risotto and garnish with the remaining chives.