Make the tangzhong: Combine water, milk and flour in a medium saucepan. Whisk until combined and no lumps remain. Place the saucepan over medium heat and cook the mixture, whisking constantly, until it thickens, about 1-2 minutes. Set aside to cool.
Make the dough: While the tangzhong is cooling, begin preparing the rest of the ingredients for the dough. Whisk yeast, cardamom, salt, sugar and flour together in a large bowl. Set aside.
Attach the dough hook or dough roller to the mixer. Add melted and cooled butter, slightly warm milk, egg and the cooled tangzhong (it can be slightly warm to the touch). Mix on medium low until fully combined. Gradually add dry ingredients and mix until a dough begins to form.
Increase mixer speed to medium and knead mixture for 3-4 minutes or until dough is slightly tacky but not sticky and clears the side of the bowl. It’s okay if it’s sticking to the bottom of the bowl slightly. You can also mix and knead the dough by hand but it will take longer, more like 8-10 minutes.
Cover the bowl with plastic wrap and allow the dough to rise for 2 hours or until 1 ½ or 2 times its original size. The time will largely depend on the temperature of your kitchen.
Once dough has risen, line a baking sheet with parchment paper and divide the dough into 12 equal pieces. Working with one piece at a time, gather up the edges of the dough into a rough ball shape, pinching the dough where the edges come together to create a “bellybutton”. Place the ball, bellybutton side down, on a clean kitchen counter. Cupping the ball with your hand so that your palm is lightly resting on the dough and your fingertips are resting on the counter, make small circles with the dough until a tight ball is formed. Place the ball on the baking sheet. Repeat with remaining pieces of dough.
Cover lightly with plastic wrap and let rise at room temperature for 45 minutes.
Meanwhile, preheat the oven to 400 degrees. Combine egg and 1 tablespoon water to create an egg wash. Uncover the buns and brush each bun with the egg wash. Bake at 400 degrees for 12-16 minutes or until the buns are golden brown. Remove from the oven and transfer to a wire rack to cool completely.
When you are ready to serve, prepare the whipped cream. Place the cream in the bowl of a stand mixer. Using the whisk attachment, whisk the cream on medium-high speed until it begins to thicken. Add sugar and continue whisking until the whipped cream is fluffy and can hold medium to stiff peaks.
Using a serrated knife, slice off the top third of each bun and set the “lid” aside. Spread a generous spoonful of jam over the bottom portion of the bun, then dollop or pipe whipped cream on top. Gently place the bun lid back over the cream. Repeat with the remaining buns, dust the tops with powdered sugar, and serve immediately.
Notes
To substitute active dry yeast for instant: While this recipe calls for instant (or rapid rise) yeast, you can certainly substitute active dry yeast for the instant by proofing it in the warm milk for about 10 minutes prior to adding it to the dough. The amounts stay the same.To make ahead: Either let the dough rise at room temperature until about double in size and then transfer the dough to a 9x13 baking dish and cover it tightly with plastic wrap. Store in the refrigerator until you are ready to shape the buns and proceed with the recipe (up to 24 hours). OR, shape the buns as directed the night before baking and wrap with plastic wrap. Transfer to the refrigerator until you are ready to bake them the following morning. Be sure to give them 45 minutes or so to warm at room temperature before popping them into the oven.To store: These buns are at their very best just after baking, but should you have leftovers, store them on the countertop in an airtight container for up to 2 days. Freeze for longer storage (see below for instructions).To freeze: Once the buns have cooled completely, pop them in a freezer bag or other freezer-safe container and tightly seal. They will keep for about 3 months in the freezer.