In a small saucepan, whisk together 2 Tbsp flour and ½ cup milk until smooth and no lumps remain.

Cook over medium heat, whisking constantly, until the mixture thickens to a paste that leaves visible lines when you whisk through it. This takes 2–4 minutes.

Transfer to a small bowl and let cool to room temperature, about 20 minutes. You can also cover and refrigerate until ready to use.

In a small bowl, whisk the warm ¾ cup milk and sugar until dissolved. Sprinkle yeast over top and let sit for 5 minutes until foamy.

In the bowl of a stand mixer fitted with the dough hook, combine both flour and salt. Add the cooled tangzhong, milk-yeast mixture, melted butter, vanilla bean paste, and eggs. Mix on low speed until a soft dough forms.

Knead on medium speed for 5–8 minutes until the dough is smooth and elastic. Gradually add the softened butter, one tablespoon at a time, until fully incorporated. The dough should be smooth, elastic, and slightly tacky but not sticky.

Adding butter after the gluten develops keeps the dough elastic, like traditional brioche.

Place the dough in a greased bowl, cover with plastic wrap or a damp towel, and let rise in a warm place until doubled in size (about 1-2 hours).

For best flavor and easy handling, refrigerate the dough for 2–8 hours or overnight (after the first rise). The cold dough is much easier to roll out.

In a small bowl, mix together the softened ½ cup butter, brown sugar, cinnamon, vanilla bean paste, and cardamom until well combined into a spreadable paste. Add vanilla extract if using.

Turn the chilled dough out onto a lightly floured surface. Roll into a 16×12-inch rectangle, with the long edge facing you.

Spread the cinnamon-sugar butter mixture evenly over the entire surface of the dough, leaving a ½-inch border at the far long edge.

Using a pizza cutter or sharp knife, cut the rectangle into 12 strips (each about 1⅓ inches wide), cutting along the short side so you have 12 long strips.

Starting from one short end, roll each strip individually into a spiral. Pinch the end to seal.

Pour heavy cream into the bottom of your prepared 9×13-inch baking dish. Arrange the rolls cut-side up on top of the cream, spacing them slightly apart (they'll expand and touch as they rise).

Cover loosely with plastic wrap or a clean kitchen towel and let rise in a warm place for 45–60 minutes, until puffy and almost doubled in size.

After shaping and arranging the rolls in the pan with cream, cover tightly with plastic wrap and refrigerate overnight.

In the morning, remove from the refrigerator and let the pan sit at room temperature for about 45 minutes to take the chill off before baking. They should look puffy.

Preheat oven to 350 °F.

Remove the cover and bake for 23-25 minutes, or until the rolls are golden brown on top and the centers register about 190°F on an instant-read thermometer. Let rest in the pan for 5 minutes before frosting or serving.

In a medium bowl, beat softened cream cheese and butter together with a hand mixer or wooden spoon until smooth and creamy.

Add powdered sugar and vanilla extract, mixing until combined. Thin with 2–4 Tbsp milk or heavy cream until you reach your preferred consistency.

Spread generously over warm rolls for a gooey glaze, or wait until rolls are slightly cooled for a thicker frosting layer.