Secret ingredient in a spaghetti bolognese?

I was talking to a friend the other day, who puts a teaspoon of Cocoa powder in his spag bol, my mum puts Carrots in hers, I put balsamic vinegar in mine.

What's your weird secret ingredient?

Edit- I have been thoroughly educated about how to cook bolognese tonight!

Edit 2 - I think there's enough different versions here to keep me in bolognese for years lol