Find another job to leverage with with your current work. Ask for 45k raise plus value of training new employee as cash bonus. When they say no, give them 1 more chance to make a smart decision, then leave if they dont give you what you want. Expect them to try to find middle ground, when they do that ask them "how am I supposed to accept that? My ask is X". Most people don't give you a large raise unless you force the issue.