Put margarine in a 9 inch round glass or plastic layer cake pan. Microwave on HIGH 40 seconds, until melted. Stir in crumbs and pat on bottom of pan Put caramels in a 1 quart casserole with evaporated milk. Microwave on HIGH 2-3 minutes, until melted. Pour on crust and press pecan pieces into it. Refrigerate. Put cream cheese in a large glass mixing bowl with 1/2 cup chocolate chips. Microwave on 50% (MDM) 3-3 1/2 minutes, until cheese is softened and chips are melted. Add sugar and vanilla; blend with an electric mixer. Add egg and blend. Pour on top of caramel layer in cake pan. Rotating twice during baking, microwave on 70% (MDM-HIGH) 10-11 minutes, until center still juggles slightly. Cool and refrigerate. Combine remaining chips and 2 tablespoons milk in a 2 cup glass measure. Microwave on HIGH 1-2 minutes, until chips are melted. Stir until smooth and spread on top of cheesecake. Top with pecan halves. NOTE: Assembled cheesecake can be baked in a 350 degree pre-heated conventional oven for 40 minutes.