Preheat the sous vide water temperature to 133℉ and set the timer for 20 minutes.
Lay the lobster tails flat on the counter. Then, insert two wooden skewers from the top end. Drive them slowly through until they come out at the tail end. Try to keep them as close to the shell as you can.
Fill a second pot with water and bring to a boil.
Submerge the lobster tails in the boiling water, and then remove the pot from the heat.
As you let the lobster tails rest in the hot water for at least 2 minutes, prepare an ice bath. You can do this either by placing ice in a large bowl or adding cold water. After 2 minutes, take out the lobster tails from the hot water and place them in the ice bath.
Pull out the skewers, then gently remove the shells using kitchen shears. Mix 4 tablespoons of butter with all the garlic, salt, and pepper in a skillet over medium heat.
Keep stirring for a couple of minutes or until the butter turns brown. Now move to a small bowl.
Place each lobster tail in a vacuum-seal bag. Divide the butter mixture among all 4 bags.
Submerge the 4 bags in the sous vide water bath and leave to cook for 20 minutes.
Take the remaining 4 tablespoons of butter and brown them in a skillet over medium heat. This should be done a few minutes before the lobster tails are done.
Once cooking time is up, open each bag and pour out the liquid contents only into the skillet and stir to combine.
Transfer the mixture to a sauceboat or a bowl.
Carefully take out the lobster tails from the bags. Place each one on a serving plate and pour the butter sauce to cover it.