Prepare the tangzhong by whisking together 1/4 cup of all-purpose flour and 3/4 cup of water over medium heat until it thickens into a paste-like consistency. Set aside to cool.

In a large mixing bowl, combine 3 1/2 cups of all-purpose flour, 1/3 cup granulated sugar, 2 teaspoons instant yeast, and 3/4 teaspoon fine sea salt. Stir together before adding in the cooled tangzhong, 1/3 cup heavy cream, 1/3 cup whole milk, one egg, and 1 teaspoon vanilla paste or extract. Mix until combined.

Transfer the dough to a lightly floured surface and knead for about 5-7 minutes until smooth and elastic. Place in a greased bowl, cover, and let rise for about an hour or until doubled in size.

In another bowl, cream together 8 tablespoons of softened unsalted butter with 1/2 cup light brown sugar and 1/8 cup granulated sugar until fluffy. Mix in one large egg and 1 teaspoon vanilla extract, then fold in 1 1/4 cups all-purpose flour, 1/2 teaspoon fine sea salt, and baking powder along with both semi-sweet and mini chocolate chips.

Punch down the risen dough and roll it out into a large rectangle about 16x12 inches. Spread the chocolate chip filling evenly over the dough.

Starting from one long edge, tightly roll up the dough into a log shape and pinch the seams to seal. Slice the log into even pieces about two inches wide.

Place the sliced rolls on baking sheets lined with parchment paper, cover loosely, and let rise for another hour until puffed up.