Salted egg butter cake (Recipe adapted from the net with some modifications)

Ingredients
4 egg yolks
250g unsalted butter (I used Lurpak)
200g self raising flour
60g salted egg powder (I used Knorr)
50g milk 
2 tsp vanilla extract

4 egg whites
180g sugar

Method
1. Preheat oven at 160ºC
2. Beat egg whites and sugar till stiff peaks form.
3. In another mixing bowl, beat butter until creamy, add egg yolks one by one and mix well. Add vanilla extract and milk, combine well.
4. Fold half of the egg whites and mix well, then fold the remaining egg whites. 
5. Add and fold the sieved flour and salted egg yolk powder, mix well.
6. Pour batter into lined pan and tap a few times on the table. 
7. Bake for 25 minutes, turn the temperature down to 150ºC, lightly cover the cake with aluminum foil and bake for another 45 minutes or until skewer comes out clean.

The Paste
50g unsalted butter
1 cup salted egg yolk powder
1/4 cup sugar (to taste)
1/2-1 cup evaporated milk

Method
1. Using low fire, melt the butter in a saucepan. 
2. Add salted egg yolk powder, sugar and evaporated milk and bring it to boil (Add more evaporated milk if the sauce is too thick or add more salted egg yolk powder if it's too watery).
3. Let it cool completely.