Combine raisins and rum in measuring cup, cover and let soak for at least 30 minutes.
Spread hazelnuts on baking sheet and toast in 350°F (180°C) oven for 10 minutes. Cool and chop medium-fine by hand or with food processor.
Using slotted spoon, remove raisins from rum and mix with hazelnuts and brown sugar. Reserve rum.
Wash and core apples generously, leaving 1/2-inch (1 cm) on the bottom intact for base. Score apples around middle to allow them to expand without splitting as they bake. Pack cavities with hazelnut mixture, heaping any excess on top. Place in baking pan large enough to accommodate apples (a 11- x 7-inch/1.75 L dish is perfect).
Combine reserved rum, honey and butter and ladle about a third over apples. Bake in 350°F (180°C) oven for 50 to 60 minutes or until apples are tender. Baste apples twice during cooking, each time adding a third of the rum sauce.
Serve hot, warm or at room temperature.