Mix together the peanut butter and tahini until well blended. Add the maple syrup and heat to boiling, stirring occasionally. Add the Grape Nuts and mix thoroughly. Spread evenly in a lightly oiled 13 x 9 pan. Sprinkle wheat germ on top if desired. Chill until firm and cut into bars.
Variation: Instead of the tahini, use another 1/2 cup peanut butter. I probably would've done this myself, but I had some tahini that I wanted to get rid of :-)