Coffee cheesecake with candied walnuts

Ingredients

• 125 gram chocolate wheaten biscuits
• 125 gram vanilla wine biscuits
• 100 gram walnuts, toasted
• 120 gram unsalted butter, melted
• 180 gram brown sugar (about 1 loosely packed cup)
• 400 gram cream cheese, softened
• 300 gram sour cream
• 4 eggs
• 2 tablespoon plain flour, sifted
• 300 millilitre cream, lightly whipped, plus 200ml extra, to serve
• 1 teaspoon vanilla extract
• 1/3 cup strong espresso, cooled
• candied walnuts, to serve (see below)
• Candied walnuts
• 1/2 cup sugar
• 2 tablespoon water
• 1 cup toasted walnut halves
• pinch of salt