Preheat the oven to 350F (175C) and line the muffin pan with paper liners.

Into a mixing bowl, sift the flour, salt, and baking powder. Set aside.

Pour the oil in a microwave save bowl, add the butter, and heat just until the butter has melted. Set aside.

Place the eggs and sugar in a stand mixer fitted with a whisk attachment (you can also use a hand mixer). Whip on high until the sugar has dissolved and the mixture turns pale yellow and has tripled in volume. It will take approximately 5 minutes depending on what mixer you use.

Then, slowly pour in the oil and butter mixture while whisking on low.

Using a rubber spatula or while the stand mixer is running on low, fold in the dry ingredients in three parts alternating with the milk. Start and end with dry ingredients.

Fill the cupcake liner ⅔ full and bake for 20-22 minutes or until a toothpick inserted in the middle of a cupcake comes out clean. Remove from the oven and leave to cool down completely before frosting.

Place all the ingredients in a stand mixer fitted with a whisk attachment (or you can use a hand mixer) and mix on low until no dry powdered sugar is left. Then, beat on medium until reaching a homogenous consistency. Scrape the sides of the bowl and mix on high until thick and fluffy.

Mix the frosting with a rubber spatula to remove air bubbles. Then, place the mixture in a piping bag with your favorite piping nozzle and decorate your cupcakes when they have completely cooled to room temperature.