To caramelize sugar, in a large skillet cook the 2/3 cup sugar over medium-high heat until sugar begins to melt, shaking skillet occasionally. Do not stir. When sugar starts to melt, reduce heat to low and cook about 5 minutes or until all of the sugar is melted, stirring with a wooden spoon as needed. Pour caramelized sugar into bottom of a 9-inch deep-dish pie plate; tilt pie plate to coat bottom. Let stand for 10 minutes.
Meanwhile, preheat oven to 325 degrees F. In a large bowl beat cream cheese with an electric mixer on medium to high speed for 30 seconds. Add the 1/2 cup sugar; beat until combined. Beat in sweetened condensed milk until combined. Beat in eggs, half-and-half, and vanilla until smooth.
Place pie plate in a roasting pan on an oven rack. Pour egg mixture into pie plate. Carefully pour boiling water into roasting pan around pie plate to depth of 1 inch. Bake about 70 minutes or until top is lightly browned and a knife inserted near center comes out clean.
Carefully remove pie plate from water. Cool in pie plate on a wire rack. Cover and chill for 8 to 48 hours.
To unmold, use a knife to loosen edge of flan. Invert a serving plate with a rim over pie plate; turn over serving plate and pie plate together. Remove pie plate. Spoon any caramelized sugar remaining in pie plate onto flan. If desired, garnish with Sauteed Plantain Slices and nuts.
Sauteed Plantain Slices
Peel and slice one small plantain. In a small skillet melt butter over medium-high heat. Add plantain slices. Cook about 8 minutes or until lightly browned, stirring occasionally; cool.