12 tablespoons (1-1/2 sticks) unsalted butter, melted and cooled.
Apricot jam layer:
1/4 cup apricot preserves
2 cups sugar
1 cup plus 3 tablespoons heavy cream, at room temperature
1 tablespoon unsalted butter
1/2 teaspoon pure vanilla extract
1/2 teaspoon kosher salt
2 tablespoons slices almonds
7 dried apricots, cut into thin strips
1/4 cup golden raisins
Heat the over to 350ºF, with a rack in the middle. Line a 20 centimeter square baking pan with two sheets of foil, shiny side up, crisscrossing them to leave an overhand on all sides. Lightly spray with nonstick cooking spry or grease with butter.
Spread the nuts on a baking sheet and bake until fragrant and toasted, 10 to 12 minutes. Remove the nuts from the over and let cool for ten minutes.
Set aside 16 nuts for garnish and wrap the remaining nuts in a clean kitchen towel. Reduce the over temperature to 325ºF.
Rub the warm nuts in the towel to remove most of the skins (it’s OK if they don’t all come off). Transfer to a food processor and pulse until very finely chopped, then transfer to a medium bowl.
Add the flour, sugar, and salt to the chopped nuts and whisk to combine. Add the cooled melted butter and stir to combine. Turn the mixture out into the prepared baking pan and press it evenly over the bottom and six millimeters up the sides. Bake until lightly golden, 30 to 35 minutes. Let cool completely on a wire rack. (The crust will firm up as it cools.)
Apricot jam layer:
Heat the preserves in a small saucepan over low heat just until warm to the touch and loose enough to spread easily, one to two minutes. Brush the warm jam over the cooled crust. Set aside.
Place the sugar in a large deep saucepan. Slowly and evenly pour 1/4 cup plus two tablespoons water over the sugar to moisten it evenly. Heat over medium-low heat, undisturbed, until the sugar is a deep amber-brown, 12 to 15 minutes. Brush down the sides of the pan with a wet pastry brush if necessary to remove any sugar crystals.
In a medium saucepan, heat the cream, butter, vanilla, and salt until the cream is warm and the butter is melted. Remove from the heat.
Towards the end of cooking the caramel, gently swirl the pan to ensure that the sugar caramelizes evely. If at any point the sugar bubbles so much that you can't see the color, reduce the heat to low.
Remove the pan from the heat. Carefully add the cream mixture (the mixture will bubble up), stirring with a whisk or silicone spatula to combine. Fit the pot with a candy thermometer and return it to medium heat. Cook the caramel, whisking occasionally, until it reaches 245 F, four to six minutes. Remove from the heat and immediately pour it over the hazelnut crust, tilting the pan as needed to spread it evenly. Let cool on a wire rack for one hour, then refrigerate until the caramel is set, at least one hour, or overnight.
Using the foil, remove the bar from the pan. Peel off the foil, then cut the bar into 16 squares. Decorate the bars with the sliced almonds, apricots, reserved hazelnuts, and raisins to make flowers, or as you like. The bars keep, covered and refrigerated, for up to one week. Serve at room temperature.