Melt chocolate and butter in heavy medium saucepan over low heat, stirring until smooth. Mix in crushed cookies and whiskey. Pour into bowl. cover and chill until firm, about 45 minutes.
Line cookie sheet with foil. Drop truffle mixture by tablespoons onto foil, spacing apart. Freeze 15 minuts. Roll each between palms of hands into smooth round ball. Sift cocoa powder and sugar into shallow dish. Roll each truffle in cocoa mixture.
Can be prepared 1 week ahead. Covered and refrigrated in air tight container.
Let stand 15 minutes at room temperature before serving.