Fudge Upside-down Cake

*FUDGE UPSIDE-DOWN CAKE*
Has a similar texture to a rich brownie. The fudge sauce sinks to the bottom during baking, but is spooned over the cake for serving, top the works with a scoop of vanilla ice cream. Serves 12

2 cups	Flour	500 mL
1/4 cup	Unsweetened cocoa powder	50 mL
4 tsp	Baking powder	20 mL
1/2 tsp	Salt	2 mL
1-2/3 cups	Sugar	400 mL
1 cup	Coarsely chopped walnuts	250 mL
1 cup	Milk, room temperature	250 mL
1/4 cup [1/2 stick]	Unsalted butter, melted	50 mL
2 tsp	Vanilla	10 mL
1 ounce	Unsweetened chocolate, melted	30 g
SAUCE
1 cup	Sugar	250 mL
1 cup	Firmly packed dark brown sugar	250 mL
1/2 cup plus 2 tbsp	Unsweetened cocoa powder	150 mL
1-3/4 cup	Hot water	425 mL
Preheat oven to 325°F [160°C] CAKE Generously butter 9x13 inch [23x33 cm] baking dish. Stir first 4 ingredients into large bowl. Mix in sugar and nuts. Whisk milk, butter and vanilla in medium bowl. Add to dry ingredients and beat well. Beat in chocolate. Spoon batter into prepared dish; smooth top. Set aside while preparing sauce. SAUCE Mix both sugars and cocoa in medium bowl. Gradually add hot water and stir until smooth. Gently pour sauce over back of spoon onto cake batter, covering completely. Bake until cake is firm to touch and top is well browned, about 50 minutes. Let cake cool slightly.