Place cream cheese in small glass bowl of electric mixer or in a
1-quart microwave-safe bowl. Microwave on HIGH (100%) 15 to 25
seconds or until cream cheese has softened.
Add 2 tablespoons of the sweetened condensed milk and the vanilla.
Beat on low speed just until mixture is smooth; set aside.
Place remaining sweetened condensed milk, semisweet chocolate and
butter in a 2 1/2-quart microwave-safe bowl. Microwave on medium
(50%) 2 to 3 1/2 minutes or until mixture can be stirred smooth and
is glossy, stirring twice.
Stir in pistachio nuts. Spread chocolate mixture evenly into
prepared pan. Drop cream cheese mixture, by spoonfuls, over
chocolate; swirl lightly over chocolate. Let stand until firm or
place in refrigerator.
Cut into 25 even squares by making 4 lengthwise and 4 crosswise cuts
equidistant from each other, then cut each square diagonally in
half. Store in airtight container with waxed paper between layers.
Keeps best if refrigerated.