Preheat oven to 325°F (163°C). Line a 12-cup muffin tin with paper liners.
Mix crumbs and melted butter; press about 1 tbsp into each liner to form crusts.
Beat cream cheese and sugar until smooth. Add egg, sour cream, vanilla, and salt; mix until combined.
Fold in 1/2 cup Nutella gently to create a marbled batter.
Divide batter among crusts, filling each about 3/4 full. Swirl extra Nutella on top if desired.
Bake 15–18 minutes until centers are set. Cool, then chill at least 2 hours before serving.
Top with chips or hazelnuts and a drizzle of warmed Nutella.