Having

export class AppComponent {

  private getMyVar(n: number){
    return Promise.resolve(n * n);    
  }

  public async getVar(n: number): Promise<number> {
    let result = await this.getMyVar(n);
    return result;
  }
}

how do you call the getVar from the HTML template?

I tried

<p>getVar = {{ this.getVar(9) | async }}</p>

but this does not seem to work. The CodePen here