You should tell him about pulsed coherent 60ghz radars from Sparkfun(based on the XM125 from acconeer), they may be able to work through peanut butter to find t

You should tell him about pulsed coherent 60ghz radars from Sparkfun(based on the XM125 from acconeer), they may be able to work through peanut butter to find the level in the vat(they can see through walls).