• Preheat oven to 175c | 350F. Line a 7x10-inch baking pan with baking/parchment paper. Set aside.

For Caramel:

• Add brown sugar to a small nonstick saucepan over medium-high heat. Stir with a wooden spoon until sugar begins to melt.
• Lower heat and add butter, 1 tablespoon at a time, continuously stirring until melted and smooth.
• Remove from heat and slowly stir in cream and salt until caramel is smooth and glossy.
• Allow to cool slightly
  

For Blondies:

• Cream together butter and sugar until light and creamy. Add in eggs and vanilla. Whisk again until smooth. Add in the flour and salt, mixing slowly until just combined. Gently fold in the caramel sauce until it has swirled trough the batter and pour half of the batter into the prepared baking pan.
• Drop teaspoonfuls of Nutella onto the batter in a single layer. Spread lightly with the back of a metal spoon (or your fingertips). Cover evenly with remaining batter.
• Bake for 25 minutes or until a toothpick inserted into the middle comes out clean. Wait 10 minutes before transferring onto a wire rack to cool before slicing. (I slice mine while still warm for the 'Nutella ooze' effect).