Function as parameter in async method

I call a method containing a function:

public void DoMagicStuff(Func<T> anyfunction) {
  // do lots of magic stuff
}

This works:

public void DoNonAsyncStuff() {
  DoMagicStuff(()=> {
     AnotherFunction();
  }
}

While this does not:

public async Task<CustomClass> DoAsynStuff() {
   DoMagicStuff(()=> {
     return await DoSomethingDifferent();
  }
}

"The await operator can only be used in async functions"

How do I make this work for async methods?