In a medium, heavy-bottomed saucepan over medium heat, sprinkle the granulated sugar in an even layer. Let it melt and caramelize to a clear amber, swirling gently every 30 seconds to heat evenly.

Once the sugar is a deep amber (5–6 minutes), add butter pieces all at once and whisk vigorously until fully incorporated and smooth.

Slowly pour warm heavy cream into the caramel while whisking to prevent separation, then whisk until the bubbling subsides and the sauce is smooth.

Remove from heat, stir in vanilla extract and sea salt, and cool for about 5 minutes to avoid clumping with the powdered sugar.

Transfer the caramel to a large bowl, sift in powdered sugar gradually while beating on low, then increase to medium speed until smooth and glossy.

Beat on medium-high for 1 minute to introduce air; add extra cream or milk by tablespoon if you want a thinner texture, or more sugar for thicker piping consistency.

Use immediately or chill for 30 minutes for firmer peaks, then stir gently before piping or spreading to restore silkiness.