I was able to model the two piece bagel, made with straight line segment knife, rotated 360 degrees,
using center axis of torus unwrapped as base line for flow. The unwrapped line is also the center line of two one-turn helices with one rotated 180 degrees.
The line segment knife is swept along the two helices as rails. The sweep is the source for the flow.
The center axis is the target for the flow.
Next the torus and swept knife were divided into 4 quadrants, using circular array, because otherwise trimming doesn't seem to work properly.
Each quadrant is trimmed by the quadrant of the swept knife.
The swept knife quadrants were trimmed by the torus quadrants, to make the face where the cream cheese goes.
Appropriate parts were colored and joined, to make 2 interlocked solids, as per the first part of the video.

Maybe tonight will try the other models...

- Brian