In 1-quart saucepan, heat whipping cream just to boiling. Place white chocolate in small metal bowl. Pour hot cream over chocolate; stir until smooth. Stir in liqueur. Refrigerate about 1 hour, stirring occasionally, until very cold.
In large bowl, beat cold chocolate mixture with electric mixer on medium speed about 1 minute or until mixture begins to thicken, then on high speed until stiff peaks form. (If mixture will not beat into stiff peaks, it is not cold enough.) Continue with recipe, or store in refrigerator up to 4 hours before making tartlets.
Just before serving, spoon mousse into gallon-size food-storage plastic bag; seal bag. Cut 1/2-inch tip off bottom corner of bag; evenly pipe mousse into each fillo shell. Sprinkle each tartlet with nuts and garnish with 1 raspberry. Store covered in refrigerator.