Best Ever Chocolate Fudge Cake

Ingredients

• 1/2 teaspoon salt
• 1 1/4 cups stout
• 4 cups flour
• 1 1/3 cups unsalted butter
• 2 1/4 cups unsalted butter, at room temperature
• 4 large eggs
• 1 cup cocoa powder
• 4 tablespoons mayonnaise
• 2 1/4 cups brown sugar
• 1 cup buttermilk
• 4 1/2 cups powdered sugar
• 1 tablespoon vanilla bean paste
• 1 1/2 teaspoons baking soda
• 2 teaspoons baking powder
• 12 ounces dark chocolate