• Preheat oven to 370 F. Line a metal baking pan with parchment paper, letting the sides hang over the edge. Use a 9 x 9 inch pan for a thicker and chunkier cookie bar or a 9 x 13 inch pan for a more traditional thin Nussecken.

Cookie Base

• In a large bowl, whisk together the flour, sugar, baking powder and salt. Cut the butter into cubes and add the egg. Using your hands, knead the ingredients together until you have a smooth dough. It will be on the sticky side. Quickly press the dough evenly into the prepared pan.
• Spread the peach jam evenly over the cookie base.

NUT TOPPING

• Place the butter in a saucepan over medium heat to melt. Add the chopped hazelnuts and cook until toasted, 5 to 7 minutes, stirring occasionally. Add the sugar, water, vanilla extract, and salt to stir. As soon as the mixture combes to a boil, remove from the heat and stir in the ground hazelnuts until well combined. Spread this mixture evenly over the jam.
• Place the pan in the oven and bake for 25 to 30 minutes, or until the top is deep golden brown and the edges are caramelizing. Take the pan out of the oven and let cook on a rack for 15 minutes. Then cut the mass in the pan into thirds lengthwise, and then into quarters crosswise, and finally cut each piece in half diagonally, forming triangles. Leave in pan to cool.
• When the bars have fully cooled, remove from the pan using the parchment paper as a sling, and cut through the slice marks again to separate the bars fully. Return the parchment paper to the baking sheet.
• Melt the chocolate in the top of a double boiler over simmering water until tempered. Dip two sides of each triangle into the chocolate about 1/2 inch deep. Return the bars to the baking sheet, allow the chocolate to set 2-3 hours.
• When the chocolate is fully set, transfer cookies to an airtight container, where they will keep for up to a week.