HEAT 1 cup morsels and sweetened condensed milk in large, heavy-duty saucepan over medium heat, stirring constantly for 2 to 3 minutes until morsels are melted. Remove from heat. Gradually stir in half-and-half and vanilla extract.
POUR into ice cream maker. Freeze according to manufacturer's directions. Coarsely chop remaining morsels and add halfway through freezing.
POUR prepared ice cream mixture into 13 x 9-inch baking pan. Freeze for 2 hours or until almost firm. Spoon into large mixer bowl; beat until smooth but still frozen. Stir in chopped morsels. Return to pan; cover tightly. Freeze for 6 hours or overnight until firm.