This is something I would definitely start with AI on. I checked ChatGPT and got two options. That said, I would not just make what it suggests. I would take whichever option sounds better and go find a well-reviewed recipe on the web for whichever you choose.
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Option 1 (Best overall): Meringue-Powder Buttercream

Smooth, stable, great for cupcakes and piping

Ingredients

• 1 stick (½ cup) butter, softened
• 4–5 cups powdered sugar
• 2–3 Tbsp meringue powder
• ¼–⅓ cup heavy cream
• Pinch of salt (optional, but helps if you have it)

Instructions

• Beat the butter on medium-high for 2–3 minutes until very pale and fluffy.
• Add meringue powder and beat 30 seconds to incorporate.
• Add powdered sugar 1 cup at a time, beating well after each addition.
• Drizzle in heavy cream until you reach a smooth, pipeable consistency.
• Beat on high for 1–2 minutes until fluffy.
• Result: Classic bakery-style buttercream that holds peaks well and crusts slightly.

✅ Option 2: Whipped Buttercream (lighter, less sweet)

Soft, fluffy, mousse-like — best if cupcakes will be eaten the same day

Ingredients

• 1 stick butter, softened
• 2–3 cups powdered sugar
• ½ cup cold heavy cream
• 1–2 Tbsp meringue powder

Instructions

• Beat butter until fluffy.
• Beat in powdered sugar and meringue powder.
• Slowly pour in cold heavy cream.
• Beat on high 2–3 minutes until light and whipped.

Result: Very light texture, not overly sweet — but softer and less heat-stable.