|white chocolate containing cocoa butter, chopped||.|
|dark chocolate, 60% to 62% cacao, chopped||.|
Have ready a fine-mesh strainer suspended over a medium glass bowl.
In a food processor, process the white chocolate and dark chocolate until very fine.
In a 1 cup microwavable measure with a spout (or in a small saucepan over medium heat, stirring often), scald the cream (heat it to the boiling point; small bubbles will form around the periphery).
With the motor of the food processor running, pour the cream through the feed tube in a steady stream. Process for a few seconds until smooth. Press the ganache through the strainer and let it sit for about 2 hours, or until it puddles thickly and then disappears when dropped from a spatula. Cover it after the first hour to prevent evaporation.
Reheat the sauce in a double boiler set over hot, not simmering, water (or very carefully in a microwave with 3 second bursts, stirring gently to ensure that it doesn’t overheat or incorporate any air). The best consistency is at 72° to 75°F/22° to 24°C.
Serve as a dipping sauce or spoon on top of each sandwich cookie.
The sauce can be stored for 2 weeks refrigerated or 3 months frozen.