We start with a soft serve ice cream machine, and
strengthen the motor and auger which push the ice cream
out the spigot.
Then, we add a removable angled nozzle, which can be
easily locked in place over the built-in downward one.
This new nozzle is appropriately shaped so it can be easily
used for filling various and sundry cakes, pastries, and so
on and etc forth.
Et voilà, ice cream filled croissants. Preferably, fresh hot
croissants, right out of the oven, filled with creamy cold
goodness, and eaten before the temperatures even out and
the ice cream melts.
There exists prior art for the *result* (hot baked thing
outside, cold ice cream inside), such as baked alaska, or
fried ice cream, but this is an entirely different
mechanism, and allows any fillable food to be used.
On a related note, if you take a pastry which is normally
filled then baked, such as an apple turnover, and make the
steam escape holes smaller than normal, it will, after
baking, have a large empty void inside the pastry above
the filling. Combined with this idea, you can have a super
portable apple pie à la mode.