I spoke to a chocolatier recently about extruding chocolate on my printer. You need to temper the chocolate to get it to come out well. This means melting it at one temperature (55C-58C for bittersweet/dark, or 45C- 50C for milk or white), then cooling it to a precise lower temperature (31C-32C bittersweet/dark, 29C-30C for milk) while stirring it. Maintain it at that temperature for extrusion. So I think you either need a reservoir of tempered chocolate on the effector (which will be heavy), or a heated and temperature-controlled Bowden tube to feed the chocolate through.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].