[thedoc (OP)]

Daniel Spain asked the Naked Scientists:
   
Dear Naked Scientists,

Every year I enjoy these cakes at Christmas with a image made into the dough of the cookies that I then slice and cook. How is it that the image of a snowman or Santa can be consistent all the way through the tube of dough so that every slice turns into a image of a snowman on each cookie no matter how thick or thin you cut it?

Thank you,
Daniel Spain

What do you think?

[Don_1]

I am no baker, nor am I a designer of industrial food production machinery, but here's my best guess.

The mix for both the outer and inner patterned biscuit/cookie/cake or whatever will need to be fairly thick, so as not to run into each other when they come into contact. Each mixture would be fed (under pressure) into a moulding something to this effect:-

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It would come out sausage fashion at a set speed where a sharp rotary cutter would cut it into slices of the required thickness and each slice drops on to a conveyor which would feed the slices on to baking trays.

Of course, I could be wrong, maybe its just bunch of artistic Grannies!

[Sprool]

two extrusion tubes, one inside the other, with suitable cross-section profile to make the desired design, both forcing different coloured dough out at same rate. Same as the excellent diagram above, but all in linear arrangement to maintain optimum pressure.