Mrs Ng SK's Butter Cake

Recipe sourced: Mrs Ng SK / Method by WendyinKK, thank you both of you, a keeper recipe, soft and moist

Ingredients:
230gm butter (salted), softened (cool at 18 ~ 20C, not glossy) (I mixed with margerine)
200gm eggs, no shell or 4 grade B eggs (I used 5 eggs grade C)
50gm + 150gm sugar (I used 11gm + 90gm)
200gm self raising flour, sifted (I sifted twice)
60ml milk
1 vanilla bean, seeds scraped or 1 tsp vanilla extract

Method:
Preheat oven at 180C (conventional) or 170C.
Prepare a 8" square pan, Line the base and grease the sides (greasing helps the cake's sides to rise well).
Separate the eggs and place the whites into a medium sized bowl (6 cup capacity).
Beat egg whites until soft peaks, gradually add 50g (11gm) sugar and beat until stiff.  Set aside.
Cream butter and 150gm (90gm) sugar until pale and fluffy.
Put in vanilla bean seeds and beat for a while.
Put in egg yolks one by one and beat well after each addition.
Put in half the flour and mix on low speed until incorporated.  Put in milk in 2 additions and mix until well incorporated.  Mix in balance of flour.
Put half the egg whites in and mix on low speed.
Pour the balance of egg whites in and FOLD.
Pour batter into pan and level.
Bake for 45 minutes or until skewer comes out clean.
You may reduce oven temperature to 150C for the last 15 minutes because the top seems to getting too brown.
(Note: You may used butter in the stand mixer and egg whites with the hand mixer)