If starting with sweetened condensed milk and not dulce de leche, make your own dulce de leche by removing labels from the cans, placing them in the pot, covering with water by about 3 inches and simmering for 2 hours over low heat. Then, remove from water and allow to cool completely.

To a bowl of a mixer add 7 egg yolks, 4 tbsp sour cream and quickly mix with the paddle attachment until combined. Meanwhile, mix 1 tsp baking soda and 1 tbsp white vinegar and stir until the foam subsides, then add to the egg yolks and sour cream and mix for about 30 seconds on low-medium speed.

Add 350 g of room temperature butter or margarine and beat for another 30 seconds to combine.

Next, add 3 cups of flour and stir to bring together into a dough. Form 10 balls. Wrap in plastic. Refrigerate for 40 minutes.

If making a round 10-inch cake, divide the dough into 10 balls.

If making a rectangle 12"x18 inch cake, divide into 4.

Combine hot water with instant coffee, stir to dissolve coffee. Set aside and allow to cool.

Whip room temperature butter until fluffy and pale in color, about 5 minutes, scraping down the bottom of the bowl several times throughout.

Add room temperature condensed milk, by pouring the condensed milk down the side of the bowl while the mixer is running. Do not over whip or the cream will separate.

Add the dissolved coffee and carefully fold to incorporate.

Place egg whites into a clean (no traces of fat, or it will not whip up) bowl and whip until frothy, about 30 seconds. While continuing to whip, add sugar in a continuous stream. Continue whipping for about 15-20 minutes until the meringue is glossy in color and stiff.

Work with 1 dough ball at a time. Place a damp towel on your working surface and top it with a round 10 inch round upside-down baking pan or a 12"x18" rectangle jelly roll baking pan. Now roll the dough directly onto the back of the upside-down baking pan.

For a rectangle cake, alternatively, you can lightly mist your working surface with water, then press a piece of an aluminum foil slightly longer than the base of the baking sheet (about 12"x20"). The water will help the foil to adhere and not move as you roll the cake layer out. Now place one dough ball and roll it out to about 12x18 inches. The dough will be super thin and almost transparent.

Spread about 1/10th of meringue on top of the rolled out dough or 1/4th of the total amount if making a rectangle cake.

Sprinkle with 1/10th or 1/4th of the walnuts respectively.

If you rolled the cake layers directly on foil, slide a baking sheet underneath and transfer to the oven. Otherwise just transfer the cake to the oven.

Bake for 6 minutes at 380F, then lower the temperature to 220F and bake another 15-16 minutes (the cake underneath the meringue should stay golden in color, not burnt). Make 9 or 3 more cake layers in this manner, respectively.

Remove from the oven and allow to cool. Be very careful with the cake layers as they are extremely fragile.

Slide a flat cookie sheet under 1 of the cake layers and transfer it to on top of the dollop of frosting. Press lightly to adhere.

In a zig-zag pattern spread 1/10th or 1/4th of the frosting on top of the cake, leaving the zig-zag lines about 1/2 inch apart. Add the second layer of cake and pipe the cream in a zig zag pattern going in the opposite direction to the first. Continue layering the cake and alternating the direction of the zig zags. Invert the top layer meringue side down.

If making a rectangle cake, split the cake down the middle into two halves and stack them to give you an 8 layer cake.

Trim the sides of the cake with a serrated knife to even them out. If you leave the cake in the fridge for a couple of hours being trimming, it will be a lot easier. If pressed for time, forgo the refrigeration time.

Combine 3/4 cup hot cream, with 2 tablespoons corn syrup & 3/4 cups chopped dark chocolate. Let sit for 2 minutes. Stir to make a smooth ganache.

When frosting the cake, place the last layer bottom side up, meringue side down.

Whip 1.5 cups whip cream with 2-3 tablespoons sugar until stiff peaks. Or use 3 cups of Cool whip instead.

Cover the cake entirely in the prepared whipped cream or cool whip. Pour the prepared chocolate ganache over the cake and spread around the top, carefully coming close to the edges and allowing it drizzle down.