Spray a 1 1/2 - to 2-quart casserole dish that fits into your pressure cooker with cooking spray. Prepare the dish with a "helper handle" to enable you to lift the dish out of your pressure cooker: Cut two two-foot lengths of aluminum foil, and fold them lengthwise to make two long straps. Cross one over the other and staple in the center to make an x-shaped handle. Place the bowl on top of the "x"

In a large bowl, combine the flours, baking powder, baking soda, salt, and cocoa, and mix well.

In a medium bowl, combine the sugar(s), flax, water, applesauce, vinegar, and vanilla. Let sit for five minutes, until the flax seeds get a little sticky.

Quickly stir together the wet ingredients with the dry ingredients, along with the chocolate chips, until just combined. Pour the batter into the prepared dish. Cover the dish.

Add 1 cup water to the pressure cooker. Add a trivet or rack to elevate the dish above the water. Lower the dish into the pressure cooker using the helper handles.

Lock on the lid. Bring the cooker to high pressure; cook for 22 minutes. Let the pressure come down naturally. Carefully open the cooker, turning the lid away from you. Use the helper handles to carefully remove the casserole dish, and uncover it.

Let the dish cool on a rack for at least 30 minutes, and then invert it to turn out the cake. Turn the cake back over so the top side is up. Cool and serve with desired garnishes (we used powdered sugar and raspberries).