Pastry by Saloni

For Chocolate Sponge Cake
1 Preheat and prepare pans. Set your oven to 350°F (175°C). Grease three 8-inch (20 cm) round cake pans and line them with parchment paper so the cakes don’t stick. 
2 In a small bowl, combine the sugar and orange zest. Rub the mixture between your fingers until the sugar becomes fragrant and the oils from the zest are released.
3 Make the “buttermilk” In a small bowl, combine the milk and vinegar. Let it sit for 5 minutes it will thicken slightly and look a bit curdled. This helps make the cake soft and tender.
4 Add the orange juice, oil, vanilla and orange infused sugar to the soured milk. Whisk everything together until smooth and well combined.
5 In another bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt. Sifting helps remove lumps and keeps the cake light and fluffy.
6 Slowly add the dry ingredients into the wet mixture. Mix gently until just combined don’t over mix or the cake may turn dense. Divide the batter evenly among the three pans. Bake in the preheated oven for 20–22 minutes, or until a toothpick inserted in the center comes out clean.
7 Let the cakes cool completely in the pans for 30 minutes, then carefully invert them on a wire rack and remove cake pans to cool fully. This prevents them from breaking or sticking.
For the Chocolate Orange Truffle Ganache 
9 In a medium pot, combine the whipping cream, soft butter, and corn syrup (or honey). Warm it over medium heat until it just starts to simmer - don’t let it boil.
10 Chop the dark chocolate orange bar in small pieces and add it to bowl. Pour the hot cream mixture over the chopped dark chocolate orange in a heatproof bowl. Let it sit for about 1 minute so the chocolate starts to melt.
11 Stir the mixture gently but thoroughly until the ganache is completely smooth, glossy, and lump-free.
12 Press a piece of plastic wrap directly onto the surface of the ganache. This keeps it from forming a skin while it sets.
13 Leave the ganache at room temperature for 3-4 hours until it thickens to a spreadable consistency. If you want to speed things up, you can chill it in the fridge, but check frequently so it doesn’t get too hard.
For Chocolate Buttercream Frosting
15 Beat the butter in a mixing bowl using a electric whisk or a paddle attachement until soft and fluffy. 
17 Gradually add sifted powdered sugar in 2-3 parts and  sifted cocoa powder, mixing until smooth on low - medium speed
16 Incorporate the whipping cream and vanilla extract to create a light, airy frosting. Use room temp cream in summer months and warm cream in winter months to make a fluffy-spreadable frosting.
How to Assemble the Chocolate Orange Cake
19 Once the chocolate sponge cakes are completely cooled, level the tops if needed using a serrated knife so the layers stack evenly.
20 Use orange jam or orange marmalade for soaking. Warm it slightly with water until spreadable so it absorbs easily into the cake without tearing the sponge.
21 Place one cake layer on a serving plate or cake board. Spread a generous layer of the warmed orange jam or marmalade over the surface, allowing it to soak into the cake.
22 Make sure the chocolate orange truffle ganache is smooth and spreadable, not too firm. If it has thickened, especially during cold winter months, microwave it for 5 seconds at a time, stirring well between intervals until it reaches a spreadable consistency.
23 Spread an even thick layer (5-6 scoops) of truffle ganache over the jam-soaked cake, smoothing it gently and leaving a small border around the edges. Place the second cake layer on top and press lightly to secure. 
24 Spread orange jam or marmalade over this layer as well. Repeat soaking and filling with chocolate orange truffle ganache.
25 Apply a thin crumb coat of chocolate ganache over the entire cake to trap crumbs. Refrigerate for 20–30 minutes until set.
26 Frost the cake with a final smooth layer of chocolate buttercream frosting using an offset spatula or bench scraper.
27 Decorate with chocolate frosting and candied orange slices, orange zest, or chocolate shavings as desired.
28 For clean slices, use a sharp knife dipped in hot water, wiping it clean between cuts. Let the cake rest for about 30 minutes before serving so the layers set beautifully.
29 Store the assembled chocolate orange cake in an airtight container in the refrigerator for up to 4 days in summer or store under a cake cloche at room temperature for up to 2-3 days during winter months. For the best texture and flavor, allow the cake to sit at room temperature for 20–30 minutes before serving.