Bronwen Wyatt's Fudgy Chocolate Sheet Cake - California Prunes

Ingredients

• 1 ½ cups water (340 g)
• 1 cup packed California Prunes (186 g)
• 16 tablespoons unsalted butter (227 g)
• 2 teaspoons vanilla
• 1/2 cup bittersweet cocoa (60 g)
• 4 oz chopped bittersweet chocolate (113 g)
• ¾ cup brown sugar (154 g)
• 1 ¼ cup white sugar (205 g)
• 2 whole eggs
• 1 teaspoon baking powder
• ½ teaspoon baking soda
• 3/4 teaspoon salt
• 2 cups + 1 tablespoon all purpose flour (248 g)
• 1/2 cup buttermilk (113 g)
• 3 butter (336 g, room temperature)
• 1 can sweetened condensed milk
• ¼-1/2 cup bittersweet cocoa (30-60 g)
• ½ - 1 cup confectioner’s sugar (62-125 g)
• Heavy pinch salt
• 1 tablespoon vanilla extract