We're also going to need to hid a section of our mesh to prefvent it from being effected by our editing later on. Double-click a vertex in our inner circumference of our Icing to select the whole circumfrence. Press Control and '+' to add to the selection.

From the top of our 3D Viewport, choose Mesh, Show/Hide, then choose Hide Selected to hide our selected region.

You can show it later on by choosing Mesh, Show/Hide, then click Reveal Hiddin to show our selected region.