Banana Chocolate Walnut Cake

INGREDIENTS

• 2 1/4 cups (540 ml) all-purpose flour
• 1 teaspoon (5 ml) baking soda
• 1/2 teaspoon (2.5 ml) salt
• 1 stick (115 g) unsalted butter, softened, plus 2 tablespoons (30 ml), melted and cooled
• 1 cup (240 ml) sugar, divided
• 2 large eggs
• 1 1/4 cups (300 ml) mashed very ripe bananas (about 3 medium)
• 2/3 cup (160 ml) plain whole-milk yogurt
• 1 teaspoon (5 ml) pure vanilla extract
• 1 (3 1/2- to 4-ounce (115 g)) bar 70%-cacao bittersweet chocolate, coarsely chopped
• 1 cup (240 ml) walnuts (3 ounces), toasted , cooled, and coarsely chopped
• 1/2 teaspoon (2.5 ml) cinnamon

PREPARATION

1. Preheat the oven to 375°F (190°C) with a rack in the middle. Butter a 9-inch (23 cm) square cake pan.
2. Stir together the flour, baking soda, and salt.
3. In a medium bowl, beat together the softened butter (1 stick) and 3/4 cup (180 ml) sugar with an electric mixer at medium speed until pale and fluffy.
4. Beat in the eggs 1 at a time until blended, then beat in the bananas, yogurt, and vanilla (the mixture will look curdled).
5. With the mixer at low speed, add the flour mixture and mix until just incorporated.
6. In a small bowl, toss together the chocolate, nuts, cinnamon, melted butter, and remaining 1/4 cup (60 ml) sugar.
7. Spread half of the banana batter in the cake pan and sprinkle with half of the chocolate mixture. Spread the remaining batter evenly over the filling and sprinkle the remaining chocolate mixture on top.
8. Bake until the cake is golden and a wooden pick inserted in the center comes out clean, 35 to 40 minutes.
9. Cool the cake in the pan on a rack for 30 minutes, then turn out onto the rack and cool completely, right side up.

Cooks' note:Cake can be made 2 days ahead and kept in an airtight container at room temperature.