My best Vanilla Cake - stays moist 4 days!

Bahan-bahan (10 porsi)

• 2 cups plain / all purpose flour ((cake flour OK too, Note 1))
• 2 1/2 teaspoons baking powder
• 1/4 tsp cooking salt ((kosher salt))
• 4 large eggs ((50 - 55g / 2 oz each), at room temp (Note 3))
• 1 1/2 cups caster / superfine sugar ((granulated/regular ok too, Note 2))
• 115 g / 1/2 cup unsalted butter (, cut into 1.5cm / 1/2” cubes (or so))
• 1 cup milk (, full fat (Note 5))
• 3 tsp vanilla extract (, the best you can afford (Note 6))
• 3 tsp vegetable or canola oil ((Note 7))
• 225 g / 2 sticks unsalted butter (, softened)
• 500 g / 1 lb soft icing sugar / powdered sugar (, SIFTED)
• 3 tsp vanilla extract
• 2 - 4 tbsp milk (, to adjust thickeness)