Melt the chocolate chips in the heavy cream over low heat, stirring occasionally until blended. Remove from heat and chill in the refrigerator until cool but not firm. (Can be made ahead to this point up to 2 days ahead, but allow the cream to soften before proceeding.) Beat the chocolate cream with an electric mixer until light and fluffy, 3 to 5 minutes. Assemble the sandwiches with 2 Chocolate Wafers and a few tablespoons of ganache.
Note: If you like crispy cookies and creamy filling, make these as close to party time as possible. For a softer, ice-cream-sandwich type of dessert, make them 1 day ahead and keep them covered in the refrigerator. The wafers will absorb some of the filling and become more cakelike.