Instructions:
- Line an 8x8 inch pan with parchment paper, ensuring an overhang on two sides to create a sling for easy removal later.
- Pulse pretzels in a food processor until fine crumbs form. In a bowl, mix the pretzel crumbs, 1/2 cup peanut butter, melted butter, and granulated sugar until fully combined and sandy.
- Press the crust mixture firmly and evenly into the bottom of the prepared pan. Refrigerate for at least 15 minutes while preparing the filling.
- In a large bowl, beat the softened butter and 1 1/2 cups peanut butter until light and fluffy (about 2 minutes).
- Gradually add the sifted powdered sugar, mixing on low speed until just combined. Add vanilla extract and mix. Add heavy cream one tablespoon at a time until the filling is smooth and easily spreadable.
- Spread the peanut butter filling evenly over the chilled pretzel base. Return the pan to the refrigerator to set for about 30 minutes.
- To make the ganache, place the chocolate chips in a heatproof bowl. Heat the 1/2 cup heavy cream until just simmering, then pour it over the chocolate chips. Let sit undisturbed for 5 minutes.
- Gently whisk the chocolate and cream mixture starting from the centre until completely smooth and glossy. Pour immediately over the set peanut butter layer, spreading quickly to cover evenly.
- Sprinkle immediately with flaky sea salt, if using. Chill for a minimum of 3-4 hours, or until the chocolate topping is completely firm.
- Use the parchment paper sling to lift the dessert out of the pan. Run a hot, clean knife under water, dry it, and use it to slice the bar into 16 clean squares before serving.