Node-style callback in TypeScript

Callback.ts

class Post {
  id = "";
}

interface ICallback<T> {
  (error: Error, _?: any): void;
  (_: any, post: T): void;
}

const callback: ICallback<Post> = (error: Error, post: Post) => {
  if (error) {
    console.error(error.message);
  } else {
    console.log(post.id);
  }
};

callback(undefined, new Post());
callback(new Error("Unauthorized"));