Singleton pattern, static classes, asynchronous methods, Lazy object

public class ChocolateBoiler
{
        
    public bool Empty { get; private set; }
    public bool Boiled { get; private set; }
    public static ChocolateBoiler Instance { get; } = new ChocolateBoiler();
    private ChocolateBoiler()
    {
        Empty = true;
        Boiled = false;
    }

    public void Fill()
    {
        if (Empty)
        {
            Empty = false;
            Boiled = false;
            Console.WriteLine("Filling the boiler with milk/chocolate mixture");
        }
    }

    public void Boil()
    {
        if (!Empty && !Boiled)
        {
            Boiled = true;
            Console.WriteLine("Boiling the mixture");
        }
    }

    public void Drain()
    {
        if (!Empty && Boiled)
        {
            Empty = true;
            Console.WriteLine("Draining the boiled chocolate");
        }
    }
}