Flour, sourdough, water, salt, sugar and time. It is solid, though due to the 24 hours fermentation the tiny air bubbles make it spongy and wet inside, while it is dark, hard and crispy on the outside. With its slightly sour taste it accompanies you almost for a week if wrapped in a dump cloth. Though even when dry no crumb falls to waste: you can fry it in garlicky butter, use it for cakes, else make a soup or kvas from it.