Kahlua buns stuffed w/ mascarpone cream and salted pistacchio powder

Ingredients

DOUGH:
• 2 tsp instant dry yeast (7 grams)
• 2 tbsp (30 grams) whole milk
• 1/2 cup (65 grams) bread flour
• 1/2 cup (120 grams) Kahlua coffee liquor
• 1 1/2 cup (205 grams) bread flour
• 1 large egg + 2 yolks
• 2 1/2 tbsp (37 grams) dark brown sugar
• 2 tbsp (40 grams) molasses
• 1 tsp vanilla extract
• 1/4 tsp fine sea salt
• 4 tbsp (56 grams ) cold unsalted butter
MASCARPONE CREAM:
• 10.6 oz (300 grams) mascarpone cheese
• 3 tbsp granulated or light brown sugar
• 1/2 tsp vanilla extract
SALTED PISTACCHIO POWDER:
• 3 tbsp (30 grams) shelled roasted pistachio
• 2 tbsp (30 grams) dark brown sugar
• 1/4 tsp fine sea salt
• 1/8 tsp ground cinnamon
• 1/8 tsp ground allspice
• 3 tbsp (42 grams) melted butter for brushing

Instructions

1. START AROUND NOON TIME THE DAY BEFORE: I don't usually pre-soak my instant dry yeast but I find that they have difficulty dissolving properly in this recipe. So, mix instant dry yeast and whole milk (cold is fine) in a small bowl and set aside to soften slightly. Place 1/2 cup of bread flour in a stand-mixer bowl with dough-hook, then bring the kahlua liquor to a boil and pour it directly into the bowl. Mix on low until an even, sticky dough forms. This is a cooked "roux", which is a bread-making technique that help with moisture retention and texture with soft squishy breads like brioche.
2. Add the other 1 1/2 cup of bread flour, egg and yolks (save the whites for egg-wash later), dark brown sugar, molasses, vanilla extract and fine sea salt, as well as the softened yeast and milk. Mix on low until all the ingredients has come together evenly, then switch to medium-high speed and knead for another 5 to 7 minutes. The dough should be sticking a little to the sides and bottom of the bowl while the machine is running, but shiny and elastic. If it's dry and pulls away cleanly, add a bit more milk to adjust, or if it's wet and couldn't hold onto the hook, add a bit more flour and knead for a couple more minutes.
3. Scrape the bowl, then add the unsalted butter all at once, and knead again on medium-high speed for another 5 to 7 minutes. The dough should be extremely shiny and elastic, pulling cleanly from the sides of the bowl but sticks on the bottom while the machine is running. It should look like soft toffee candy. Cover the bowl and let rise for 9 to 10 hours in room-temperature until fully doubled. If your kitchen is warm and it's rising too fast (you see it expanding after just a couple hours), transfer and let it finish rising inside the fridge.
4. At night, once the dough has doubled, gently scrape it onto a lightly floured counter. DO NOT punch out the air, as I'm treating this almost like a sourdough. Simple divide the dough into 9 equal portions. With each portion, tuck the sides towards the center, then invert it so the seams-side's down and cup it in your palm and gently roll it on the counter in a circular motion. The friction will tighten the ball and create a smooth surface. Really butter up well a 8x8 inches square pan, or any other pans you want to bake them in (I did mine in a smaller pot and a bigger round pan). Then arrange the doughs inside with about 2 inches of space in between. Cover with plastic and let it do the second rise in room-temperature overnight (8 to 9 hours). If your kitchen is warm, let the doughs do the second rise in the fridge (if it didn't fully double in the fridge, leave it in a warm place to double before baking).
5. NEXT DAY MORNING: The doughs should have fully doubled, looking plump and airy. If you don't have time in the morning or are not serving them immediately, you can transfer it into the fridge to stop the rise, and bake when needed. Preheat the oven on 350 F/175 C. Brush the saved egg whites on the surface of the buns, then bake in the middle-rack for 25 to 30 minutes until golden browned on top.
6. Meanwhile, in a bowl, mix together mascarpone, sugar and vanilla extract until even. Transfer into a pastry bag with a fitted round tip, and set aside. In a spice grinder, pulse pistachio, dark brown sugar, fine sea salt, cinnamon and allspice until you have a fine-ground mixture (some small chunks of pistachio here and there is fine). Set aside.
7. Let the buns cool for 15 minutes, then with a small pointy knife, create a hole in the center of each buns. Insert the pastry tip into the hole and fill each bun up generously with mascarpone cream. Then brush the surface very liberally with melted butter, and sprinkle the pistachio powder on top. Serve warm.