A french tart / graham cookie dough-like clay can usually be achieved by adding ground bits of dark brown spices, e.g. ground cloves, allspice or black pepper to a pre-colored clay. But with that comes the pungent spice-y scents too, that does not, sadly exist in real cookies and tart crusts!
You can get around that by using Wood Formo; a kind of air dry clay product by Padico. Wood Formo is usually used for model-crafting and sculpting. It is very very moist, so moist that it produces water vapor within the package when the weather gets a bit warmer. :\
Wood Formo + Grace Clay
It is still very sticky to work with, and most likely you will end up getting strands of rebellious clay all over your fingers. Once you get the consistency and color you want, "ball" the clay into your palm and use your palms to fold and round it up. Avoid touching your clay-ed fingers to it and after which just wash and scrub all the residue on your fingers. It's best to allow the lump to stand outside for a while to let the moisture dry off so its workable - but not too long!