Step 1

Place the water,sugar, and corn syrup in a 3 quart sauce pan. Stir over heat until the sugar is dissolved completely. Bring to a hard boil.

Step 2

Either wash down the sides of the pan with a pastry brush dipped in cold water or put a lid on the pan for 3 to 4 minutes. Boil, without disturbing until the syrup is a dark, medium brown.

Step 3

Off heat, immediately add the butter and stir until it is melted. Mix the cream and vanilla and stir it into the pan. If some of t he cream lumps up, don't worry. Return it to medium high heat and bring it to a boil again. Boil to 232°F on a thermometer.

Step 4

When it is done, transfer it to a bowl or a storage container and let it cool to room temperature.

Step 5

It can be stored at room temperature for a couple of days or, for longer storage, refrigerate almost indefinitely. Microwave briefly to use it.

Step 6

Yield: About 2 cups.

Step 7

Preheat the oven to 375°F. Line the bottom of a 9x9" square pan with parchment paper. Spray the paper and sides of the pan with a non-stick-baking-spray.

Step 8

In a very small bowl, combine the vanilla and instant coffee. Stir to dissolve coffee and set aside.

Step 9

Sift the flour into a large bowl.

Step 10

Sift the cocoa, baking soda, baking powder and salt on top of the flour. Whisk together to mix well.

Step 11

In a smaller bowl, whisk together the milk, oil, eggs, sour cream and coffee mixture.

Step 12

Pour the liquid ingredients over the dry ingredients and stir with a spoon or fold together with a rubber spatula just until everything is mixed well. Do not over mix.

Step 13

Distribute the chocolate chunks evenly over the top.

Step 14

Pour into the prepared pan and smooth the top. Bake for 30 to 35 minutes until a tester comes out with just a bit of crumbs on it. Do not over bake.

Step 15

Cool in the pan and then turn it out onto a cake board or serving dish.

Step 16

In a small saucepan, bring the water, corn syrup and 1/4 cup (50 grams) sugar to a boil. Wash down the sides of the pan with a pastry brush dipped in cold water. Continue to boil hard until a thermometer reaches 246°F.

Step 17

In the meantime, place the egg whites, remaining sugar and vanilla in the bowl of a mixer fitted with the whisk attachment. When the temperature of the sugar syrup reaches 230° start beating the egg whites on high to the soft peak stage.

Step 18

If the egg whites reach temperature before the syrup is done, reduce the speed of the mixer to low and keep beating. Do not turn off the mixer.

Step 19

When the syrup comes to temperature, raise or lower the speed of the mixer to medium and slowly drizzle it into the egg whites, keeping it between the side of the pan and the whisk. Increase the speed of the mixer to high and beat until very thick and lukewarm.

Step 20

Place the marshmallow cream into a pastry bag fitted with a 1/2" plain tip. Pipe the meringue on a diagonal covering the entire cake.

Step 21

If using the caramel, heat about 1/2 cup in the microwave until fairly liquid. Heavily drizzle the caramel in the opposite direction of the marshmallow.

Step 22

The cake can be stored for several days at room temperature, covered.