I am doing the blender Guru latest Donut tutorial, I am trying to model the icing on top of the donut by proportionally editing it, with the option snap to face activated. The icing mesh keeps on snapping to the inside of the donut rather than the external part.
Your snap is probably set to closest. Set Snap With to Active instead. (Shift) Select last the vertex that will be the Active Element (becomes white) before moving your selection.
The way you were doing it, Blender was snapping using the (bounding box) center of all your selected vertices.