Sourdough Chocolate Cake

Name: Sourdough Chocolate Cake
Prep time: 20 min
Cook time: 30 min
Total time: 50 min
Cuisine: American
Ingredients: 220g (1 3/4 cups*) all-purpose flour; 70g (3/4 cup) cocoa powder; 1/2 tsp salt; 1 tsp baking powder; 1 tsp baking soda; 2 large eggs; 1 tsp vanilla extract; 180g (3/4 cup) vegetable oil; 100g (1/2 cup) sourdough discard starter; 130g (2/3 cup) granulated sugar; 130g (2/3 cup) soft brown sugar; 240g (1 cup) milk; 120g (1/2 cup) hot strong coffee; 226g (1 cup) butter, softened to room temperature; 300-375g (2 1/2-3 cups) powdered sugar; 30g (1/3 cup) cocoa powder; 1/2 teaspoon vanilla extract or paste; 2-3 Tbsp milk or cream at room temperature; 1/4 tsp salt; 125g (1/2 cup) pouring cream; 150g (5oz) semi-sweet chocolate, chopped