In a medium bowl, combine and sift cake flour, baking powder, baking soda and salt.
Chop the chocolate into smaller pieces. Heat in a microwave oven. Because chocolate
burns easily, every 7 seconds you must check and stir when it starts to melt. Continue until
all the lumps have melted. If you are using bitter chocolates, add 1 tablespoon of honey.
In a small bowl, mix instant coffee into 3 tablespoons of hot water until it dissolves completely.
In a medium bowl, mix butter using an electric beater. Gradually beat in sugar and salad oil.
Beat in two eggs, one at a time. Add vanilla extract and yogurt (or sour cream) and beat until
smooth. Divide the flour mixture that you prepared earlier into thirds. For each 1/3 flour
mixture, sift in and beat at the lowest setting.
Preheat the oven to 350°F (175°C). Grease an 8 x 8" square pan. Drop half of the
batter in the pan in random places, leaving parts of the pan empty.
Beat in the melted chocolate and coffee to the remaining batter. Drop in the chocolate batter
to fill the gaps in the pan. Using a chopstick or spoon, swirl the chocolate batter to create
a marble pattern. You can use a crosshatch pattern or create spirals. Smooth the top of the
batter with a spatula. Bake at 350°F (175°C) for 30-35 minutes.