WITH EmpCTE(EmpID, FirstName, LastName, MgrID)
AS
BEGIN CALLOUT A
  (SELECT EmployeeID, FirstName, LastName, ManagerID
  FROM HumanResources.Employee AS E
    JOIN Person.Contact AS C
      ON C.ContactID = E.ContactID
  WHERE EmployeeID = 12
END CALLOUT A

  UNION ALL

BEGIN CALLOUT B
  SELECT E.EmployeeID, C.FirstName, C.LastName, E.ManagerID
  FROM HumanResources.Employee AS E
    JOIN Person.Contact AS C
      ON C.ContactID = E.ContactID
    JOIN EmpCTE AS M
      ON E.ManagerID = M.EmpID)
END CALLOUT B
SELECT * FROM EmpCTE;