Mock one method on a class instead of the whole class using Moq?

I have a class

public interface IMyInterface 
{
    string MethodA();
    void MethodB();
}

public class MyClass : IMyInterface
{
    public string MethodA()
    {
        // Do something important
    }

    public void MethodB()
    {
        string value = MethodA();
        // Do something important
    }
}

I want to unit test MethodB, but I'm having trouble thinking about how I can Mock MethodA while still calling into MethodB using Moq. Moq mocks the interface, not the class, so I can't just call mock.Object.MethodB(), right?

Is this possible? If so, how?