How do I lerp an object's angle backwards?

I can lerp an objects rotation to "20" correctly. But when I want to to go the other way, say to "-20", it spins around clockwise till it gets there instead of just going backwards. How can I make sure it just goes backwards instead?

My current code: Set angle to lerp (self.Angle,HeadAngle,0.2*dt+0.1)

HeadAngle is a global variable which decides the current angle it should aim towards.

The "anglelerp()" expression worked like a charm. Thanks!