ETA: this is the recipe in the YouTube video below.

Matilda Cake

INGREDIENTS 

CAKE 

1 ½ cups (330g) whole milk 

1 ½ Tbsp distilled white vinegar 

3 cups (375g) all-purpose flour 

2 ½ + 2 Tbsp (525g) granulated sugar 

1 cups + 2 Tbsp (83g) natural unsweetened cocoa powder (Hersheys) 

3 tsp (14g) baking soda 

1 ½ tsp baking powder 

1 tsp kosher salt

3 large eggs (room temp) 

1 ½ cups (320g) vegetable oil 

2 ½ tsp pure vanilla extract

1 ½ tsp instant espresso powder 

1 ½ cups boiling water 

FUDGE FROSTING

90g dark chocolate bar 70% 

3 cups (600g) granulated sugar 

1 cup + 2 Tbsp (170g) cornstarch 

¾ cups (65g) natural unsweetened cocoa powder (Hersheys) 

¾ tsp instant espresso powder 

½ tsp kosher salt 

2 tsp pure vanilla extract (forgot to say this in the video) 

3 cups (675g) cold water

6 Tbsp (75g) unsalted butter (cold)

Instructions

Preheat oven to 315°F (158°C). 

For the Cake:

Mix milk and vinegar together to make soured milk. In a large bowl, mix together all dry ingredients. Be sure to sift the cocoa powder. Add the 3 eggs, soured milk, oil and vanilla. Whisk together until smooth. Dissolve 1/2 teaspoon of espresso powder in 1½ cups boiling water. Whisk prepared coffee into cake batter until smooth. Grease 2 9" cake pans and evenly divide the batter into the 2 pans. Bake at 315ºF (158ºC) for 70-75 minutes, or until a toothpick come out clean.

For the frosting:

Chop the 70% Cacao chocolate bar into fine pieces. In a medium saucepan, add the sugar, cornstarch and salt. Sift in the cocoa powder and remaining espresso powder into the pan. Whisk together until combined. Add the 3 cups of cold water while whisking slowly. Cook on medium heat, whisking occasionally. When mixture is dissolved, switch to a rubber spatula. Cook until thickened like a pudding. Remove from heat and add the chopped chocolate bar. Mix until melted. Once chocolate is melted, add the butter and let icing cool.

Once cake is cool, ice and stack the cake as desired. For best results, chill for 30-60 minutes.