What strange centerpiece does Pip see on the table? How does Miss Havisham explain it?

Pip after looking carefully realises that the "epergne or centrepiece ... was so heavily overhung with cobwebs that its form was quite indistinguishable." It had become rotten and seemed "like a black fungus" on which were crawling spiders.

Finally, the mystery is cleared up by Miss Havisham telling Pip who was not able to guess what it was that "IT'S A GREAT CAKE. A BRIDE-CAKE. MINE!" Before Pip is able to figure out what she meant by this, Miss Havisham catches hold of him and asks him to help her to walk around the room.

Later, in Ch.22 Herbert tells Pip how Miss Havisham was cheated on her wedding day by her fiancee: " the marriage day was fixed, the wedding dresses were bought, the wedding tour was planned out, the wedding guests were invited.The day came, but not the bridegroom." Miss Havisham obviously went into a state of shock from which she has still not recovered and she has left the wedding cake on the table to continue to rot till today. How Creepy is that???