Boston Cream Doughnuts

Ingredients

• 2 1/4 tsp or 7g yeast
• 1/4 cup lukewarm water
• 1/2 tbsp + 1/4 cup sugar, divided
• 1 cup evaporated milk
• 3 tbsp butter, softened
• 1 tsp salt
• 3 cups bread flour plus extra, about 5 tbsp
• 1 large egg, beaten
• melted butter for coating
• 4 large egg yolks
• 1/2 cup granulated sugar
• 1/4 cup cornstarch
• 2 cups fresh/whole milk
• 2 tbsp butter, unsalted
• 2 tsp vanilla extract
• 1 cup powdered sugar
• 1/4 cup unsweetened cocoa powder
• 1 tsp vanilla extract
• 3 tbsp fresh milk plus extra depending on consistency