Place the tarragon, chives, lemon zest, lemon juice, garlic, salt, and pepper in a blender and blend until the herbs are minced and the ingredients are combined. With the machine running, add the olive oil. Add the mascarpone cheese and cream and blend until mixed.
Transfer the lobster to a medium bowl. Add the herb sauce and stir to coat. Divide the lobster mixture among the sandwiches and serve immediately.