Preheat your oven to 350°F / 175°C.
Grease an 8-inch or 9-inch square baking pan with butter.
In a medium bowl, use an electric mixer to cream 1 stick (1/2 cup / 113g / 4 oz) of the softened butter with 1/4 cup (50g / 1.76 oz) of the sugar until light and fluffy.
Stir in the flour until just combined. The mixture will be dry and crumbly. Press it evenly into the bottom of the prepared pan to form the crust.
Bake the crust for 15 minutes, but no longer.
Remove it from the oven and let it cool slightly while you prepare the topping.
In a medium saucepan over medium-high heat, combine the remaining 1 cup (200g / 7.1 oz) of sugar with 1 tablespoon of water.
Cook, swirling the pan occasionally, until the sugar melts and turns a light amber color, about 5 to 8 minutes.
Carefully stir in the remaining 1 stick (1/2 cup / 113g / 4 oz) of butter, the heavy cream, and the salt. The mixture will bubble up, so be cautious.
Stir continuously until everything is combined and smooth.
Remove the saucepan from the heat and stir in the honey and the chopped walnuts.
Immediately pour the hot walnut caramel mixture evenly over the partially baked crust.
Refrigerate the pan for at least 30 minutes, or until the caramel is completely set and firm.
Once set, cut into squares or rectangles to serve. Store in an airtight container for up to 5 days.
