In a medium bowl, dissolve 2 tablespoons of yeast into 1½ cups of the half and half. Add 1½ cups of the bread flour and stir until a smooth paste forms. Cover bowl with plastic wrap and let rest in a warm spot for about 30 minutes.

Meanwhile, combine the remaining half & half and yeast in the bowl of a stand mixer fitted with the paddle attachment. Mix on low speed to combine. When the paste mixture has rested (and has risen slightly) add it to the mixer bowl along with the vanilla and egg yolks. Mix until smooth. Turn off the mixer and add 2 cups of the remaining flour, along with the sugar and salt. Mix on low for about 30 seconds or until the dough starts to come together. Add the melted butter and mix until it becomes incorporated, another 30 or so seconds.

Switch to a dough hook and gradually add more flour, about ¼ cup at a time. Knead the dough at medium speed between additions until the dough pulls completely away from the sides of the bowl and is smooth and not too sticky. You may not need all of the remaining flour. The dough will be quite soft.

Grease a large bowl with butter or cooking spray, then transfer the dough to the bowl and turn to coat. Cover with plastic wrap and allow to rise in a warm place for 30 minutes. After it has rested, gently punch down the dough and refrigerate it for at least 2 hours.

While the dough is chilling, make the pastry cream. In a medium bowl, whisk together the cornstarch and ½ cup of milk. Set aside. Combine the remaining milk and sugar in a medium saucepan; heat until the mixture just starts to bubble. Remove from heat.

Beat the whole eggs and yolks into the cornstarch/milk mixture. Pour about ⅓ of the milk mixture into the egg mixture, whisking constantly so the eggs do not cook. Return the remaining milk mixture to a boil. Pour in the hot egg mixture in a stream, whisking constantly until the mixture thickens. Remove from heat and stir in the peanut butter. Whisk until the peanut butter is melted and well combined. Add the salt, then stir in bourbon to taste. Transfer to a bowl and cover with plastic wrap. Place in the refrigerator until ready to use.

Next, make the streusel. Heat oven to 350°. Place the flour, peanut butter, sugar, brown sugar and salt in a small bowl. Add the melted butter and toss the ingredients together with a fork. Pour the mixture onto a metal baking sheet and bake for 5-10 minutes or until golden and fragrant.

Let the streusel cool on the pan completely. Crumble streusel with your fingers and mix in the chocolate chips. Reserve for later use.

When ready to cook the doughnuts, line a baking sheet with a lightly floured tea towel. Lightly flour a work surface and roll out dough to ½-inch thick. With a 3-inch pastry ring or cookie cutter, cut out rounds. Place the doughnuts on the lined baking sheet 1 inch apart and cover with plastic wrap. Let sit in a warm spot to proof until they almost double in size, about 30-40 minutes.

While you wait for the donuts to rise, heat a Dutch oven or heavy-bottomed pot with at least 2 inches of oil until a thermometer registers 360˚F. You may have to continually adjust the heat setting to keep the oil at the proper temperature.

Once the oil is hot, carefully drop in a few doughnuts at a time, taking care not to overcrowd your pot. Fry for 1-2 minutes on each side, until they turn a light golden brown. Remove with a large slotted spoon or spider strainer to a paper towel lined baking sheet. Repeat with remaining doughnuts. Allow to cool to room temperature.

Meanwhile, prepare the glaze. Combine butter, milk, corn syrup (this adds extra sheen to the glaze, but you can omit it if desired), and vanilla in medium saucepan and warm over medium heat until butter is melted. Decrease the heat to low, add the chocolate, and whisk until melted. Add the pinch of salt. Off the heat, whisk in the powdered sugar until smooth.

When ready to assemble the doughnuts, transfer the pastry cream to a piping bag fitted with a large plain pastry tip. Place the tip inside the doughnut and squeeze about 2 tablespoons of cream into each pastry. You should feel the doughnut expand slightly in your hand. Repeat until all the doughnuts are filled.

Return the glaze to low heat if it is too thick for dipping. Dip the tops of each doughnut into the glaze and allow the excess to run off. Let each donut stand for about 30 seconds, and then sprinkle on or dip in the streusel. Sprinkle on sea salt, if desired. Repeat until all the doughnuts are glazed.

The assembled doughnuts can be left at room temperature for several hours and are best eaten fresh. However, you can refrigerate and gently reheat in the microwave the next day.