Preheat oven to 350F and grease and flour three 4” cake rounds.

Whisk together flour, sugar, baking soda, salt, baking powder and cardamom in a bowl.

Add butter, and beat well with a hand mixer or in a stand mixer with the whisk attachment, until the mixture resembles fine crumbs.

In a separate bowl, whisk together egg, sour cream and oil until combined.

Pour in the flour and butter mixture, and beat on medium for 3-4 minutes. The mixture will be dry at this point.

Add in water and mix until just combined. Do not over mix.

Pour batter evenly into prepared pans. Smooth the tops with a spatula.

Bake for approx. 20 mins or until a toothpick inserted into the center comes out mostly clean.
 Place cakes on wire rack to cool for 10 mins then turn out onto wire rack to cool completely

Place egg whites and sugar into the bowl of a stand mixer, whisk until combined. 
Place bowl over a hot water bath on the stove and whisk constantly until the mixture is hot and no longer grainy to the touch or until it reaches a temparature of 165 degrees F on a candy thermometer. 
Place bowl on your stand mixer and whisk on medium-high until the meringue is stiff and cooled (the bowl is no longer warm to the touch (approx. 5-10mins)).
Switch to paddle attachment. Slowly add cubed butter and mix until smooth. Add vanilla and continue to whip until smooth.

Put aside 1/2 cup of frosting and color it with pink gel food colouring. This will be used to decorate the cake.

Trim cake tops to create straight layers.

Place one layer of cake on a cake stand or serving plate. Top with approximately 1/3 cup of frosting and spread evenly. Sprinkle crushed pistachios in between the layers.

Repeat with remaining layers and apply a thin coat of frosting all over the cake. Chill for 20mins.
 Frost and smooth the sides.

Draw a horizontal line on one side of the cake. Place 3-4 halves of the gulab jamun along the line, using the frosting to glue the gulab jamun down.

Stick the crushed pistachios to the open spaces to complete the look.

Using a Wilton 1M tip, pipe pink frosting around the top of the cake. Place 8 gulab jamun halves on top of the border face down.

Fill the centre of the frosting rim with pistachios to complete the look.