Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to make buttercream filling [title] Place the butter in a mixing bowl and beat it until it is smooth and fluffy. [step] Use a handheld mixer or a food processor with a whisk attachment. It will make things much easier.

Ending1: [title] Remove a small portion of the mixture from the mixing bowl, and transfer it to a mixing bowl. [step] Using the tines of a butter knife, spread the butter to the top of the mixing bowl. Ending2: [substeps] For a richer flavor, use a different kind of butter. Avoid butter with added sugars, as it will make your filling bitter. Ending3: [title] Beat the buttercream filling until the mixture becomes light and fluffy. [step] Use a mini setting to beat the buttercream filling. Ending4: You can use a whisk or a wooden spoon in a pinch. [substeps] For a less sweet buttercream, use salted butter.

Answer format: ending1/ending2/ending3/ending4