Hazelnut Brownie Shortbread Bars

Something everyone is going to want for the holidays.  From Food and Drink Holiday 2022

SHORTBREAD
3 cups (750 mL) all-purpose flour
3/4 cups (175 mL) icing sugar
1/2 tsp (2 mL) fine sea salt
1 1/2 cups (375 mL) unsalted butter, at room temperature, cubed
 
BROWNIE
3 bars (each 100 g) 70 per cent cacao chocolate, roughly chopped, divided
3/4 cup (175 mL) unsalted butter, at room temperature
1 1/2 cups (375 mL) all-purpose flour
1/3 cup (80 mL) Dutch-processed cocoa powder
3 large eggs
1 3/4 cups (425 mL) granulated sugar
1/2 tsp (2 mL) fine sea salt
1/2 tsp (2 mL) pure vanilla extract
1 cup (250 mL) skinless roasted hazelnuts, divided
1/3 cup (80 mL) chocolate hazelnut spread, such as Nutella
 

1. Arrange rack in centre of oven. Preheat to 375°F (191°C). Generously butter a 9 x 13-inch (23 x 33-cm) cake pan. Line with parchment, overhanging edges on two opposite sides.
 
2. For the shortbread, combine flour, icing sugar and salt in a large mixing bowl. Add butter, working in with your fingertips until fully combined. Continue working mixture, lightly kneading just until a dough comes together. Crumble over bottom of prepared pan to distribute evenly, then press into an even layer. Lightly prick all over with  a fork. Bake in centre of oven until evenly golden, about 25 minutes. Set aside.
 
3. Reduce oven to 325°F (163°C).
 
4. For the brownie, bring a pot with 1 inch (2.5 cm) water in the bottom to a boil. Chop two chocolate bars and combine with butter in a heatproof bowl. Set on top of the pot, ensuring the bowl doesn’t touch the water. Reduce heat to medium-low and let melt, stirring often, until mixture is liquid. Remove bowl from the pot and let cool 10 minutes.
 
5. Sift flour with cocoa powder in a medium bowl. Set aside.
 
6. In the bowl of a stand mixer fitted with the whisk attachment, whisk eggs with sugar and salt on medium-high speed until pale, thick and ribbony, 3 to 5 minutes. Whisk in vanilla. Remove bowl from stand mixer and using a spatula, carefully fold in melted chocolate mixture, then flour mixture, just until no streaks remain.
 
7. Finely chop 1/2 cup (125 mL) hazelnuts, then gently fold in, along with remaining chocolate bar, just until combined. Scrape mixture over prepared shortbread, smoothing top. Drop teaspoonfuls of hazelnut spread evenly over the top of the batter. Swirl with a wooden skewer, careful not to hit the shortbread base. Roughly chop remaining 1/2 cup (125 mL) hazelnuts and sprinkle evenly overtop.
 
8. Once oven has fully reduced in temperature, bake in centre of oven until brownie has set, about 50 minutes. (A toothpick inserted in the centre of the brownie base should come out with moist crumbs attached.) Transfer to a rack and cool completely.
 
9. Run a butter knife along the unlined edges of the pan to loosen. Using parchment edges, lift bars out of pan. With a sharp knife, cut lengthwise into four rows, then crosswise into eight rows to make 32 squares. (Bars will keep at room temperature in an airtight container up to 3 days.)
 

Makes 32 bars