■ Making the Brownie Batter
Chop the chocolate and butter, place them in a bowl, and melt over a double boiler. Once melted, remove from the heat and gently mix with a whisk.

Add the sugar and mix with a whisk until no longer gritty, then add the beaten egg and mix.

Add the sifted all-purpose flour and mix until no flour remains, then set aside about 1/2 tablespoon for the pattern.

Pour the batter into the prepared pan and smooth the surface with a spatula to ensure even thickness.

■ Making the Cheese Batter
In a microwave-safe container, lightly heat the cream cheese to soften, then add the sugar and egg and mix.

Put the batter into a piping bag fitted with a #3 round tip and pipe it evenly over the surface of [5].

Drizzle the reserved brownie batter with a spoon, and use a skewer to gently draw random lines on the surface to create a marble pattern.

Bake in a preheated oven at 340–355°F for about 30 minutes, being careful not to over-brown. Let cool in the pan.

Once completely cooled, remove the parchment paper from the bottom and trim about 1/5 inch from each of the four edges. Cut into desired sizes to finish.

※ For a herringbone pattern, in step [8], draw the brownie batter in parallel thin lines, and use a skewer to draw in alternating directions.

Reference wrapping for cutting into 9 pieces
http://item.rakuten.co.jp/asai-tool/gt-7/