Preheat the oven to 350ºF. Grease a 9x9 inch pan and then line with parchment paper being sure it comes up the sides, too!).
Melt the butter in the microwave in a medium glass bowl. Once melted, stir in the sugar, flour and salt. Pour into baking pan and press down to compact the crust. Bake for 15 minutes or until lightly golden. Allow to cool.
In a large bowl, beat all ingredients except Nutella until creamy. Pour into cooled crust.
Microwave Nutella in 15 second intervals, stirring often until runny. Now drizzle over the cheesecake mixture and using a toothpick, swirl in. Bake for another 15-20 minutes or until the cheesecake is set.
Remove from oven and allow to cool 30 minutes before placing it in the fridge to cool completely. Once cold, slice into bars and serve immediately. Refrigerate any leftovers in an airtight container.