<p>I have seen lots of printers that print chocolate using a syringe with molten chocolate. But, even cooler, would it be possible to print chocolate using some kind of feed system for <strong>continuous</strong> chocolate printing, so large objects and for a prolonged time, not only lasting the content of one syringe with molten chocolate ?</p>

<p>Things to consider are IMO:  </p>

<ul>
<li>How to keep the chocolate long enough in a molten, viscous state
enough to print ?</li>
<li>Chocolate needs a tempering temperature, which
means it needs to be around 32-37 degrees celsius, else it doesn't
shine but gets a dull look (or turns white after a while). </li>
<li>Chocolate
is food, so you need foodsave equipment in the whole chain that is in
contact with the chocolate.</li>
</ul>

<p>Maybe a peristaltic pump that keeps pumping the molten chocolate to the extruder, which might be a valve that can be open/closed from G-code ?</p>

Update: I found a nice article about chocolate printing:
https://all3dp.com/2/chocolate-3d-printer-all-you-need-to-know/
You are searching for chocolate extruder. I did not find one, which would fulfill all your requirements. You have to adapt each solution.
Zmorph3d Liquid paste extruder
https://zmorph3d.com/cake-and-chocolate-extruder/
According video on the page you insert chocolate in liquid form. That could be solved with heated chocolate container.
Syringe based extruders
http://www.open-electronics.org/3drag-is-now-printing-with-chocolate/
http://richrap.blogspot.de/2012/04/universal-paste-extruder-ceramic-food.html
http://www.instructables.com/id/Chocolate-Extruder-for-Ultimaker/
You can use a
2 liters syringe
. And if this is not enough then you can refill during print.
Convert pellet extruder
Printing from chocolate pellets is simpler then printing from plastic pellets. Therefore if you use foodsave parts to build such a extruder then this is useable for you.
https://www.youmagine.com/designs/universal-pellet-extruder-reprap-3d-printing
Cooling
3DRAG CHOCO (Chocolate 3d printer) Cooling system explained
Shop
by Open-Electronics
Extrude for chocolate
Syringe Heater for 3Drag chocolate printer