Thin out the miso with buttermilk by slowly incorporating buttermilk into miso a couple tablespoons at a time, stirring and mashing until homogeneous

Continue adding buttermilk until half is incorporated, then whisk the remaining buttermilk into the miso mixture

In a large mixing bowl, whisk together all-purpose flour, granulated sugar, baking powder, and baking soda until evenly incorporated

Add butter cubes to the dry ingredients and toss in flour to coat

Smash the butter into flat pieces using your fingertips until no chunks are larger than the size of a pea

Slowly stream in the wet ingredients while stirring with a fork, pouring around the bowl to ensure even distribution

Fold the mixture with a spatula or bench scraper about 5-6 times until evenly incorporated

Turn the dough out onto a floured work surface and push into a half-inch thick rectangle

Cut the dough into four equal quadrants and stack them on top of each other

Roll out the stacked dough to an 8.5 inch by 8.5 inch square, rotating as you roll

Trim the uneven edges and cut the dough into 2 inch by 2 inch squares

Freeze the biscuits for about 15 minutes to firm up the butter

Preheat oven to 425°F

Brush the tops of the biscuits with melted butter and sprinkle with cracked black pepper

Reduce oven temperature to 375°F and bake for 20-25 minutes until bottoms are dark brown and tops are golden brown

Cool on counter for about 5 minutes before serving

Store unneeded biscuits in the freezer for up to a month and bake directly from frozen, adding 3-5 minutes to bake time