To make homemade dulce de leche, remove and discard labels from cans of condensed milk. Place the unopened cans into a large saucepan and pour in enough water to cover by 1 or 2-inches. Bring water to a boil over high heat, then reduce heat to medium, cover, and simmer for 3 hours. Drain, and allow cans to cool to room temperature before opening.

Meanwhile, cook the puff pastry sheets according to package directions and allow to cool to room temperature. Pour the dulce de leche from one can evenly over a sheet of puff pastry. Place a second sheet of puff pastry over the first, then pour on the remaining can of dulce de leche. Top with the remaining puff pastry sheet, then cut into 12 triangles.

Heat a grill pan over medium-high heat and oil with cooking spray, or preheat an outdoor grill for medium-high heat. Grill the pineapple rings until warm and nicely marked.

Serve each triangle on a dessert plate garnished with a grilled pineapple slice and a scoop of citrus sorbet.