Chill Champagne flutes in the fridge or fill them with ice water for a few minutes.

Place the sugar cube in a small mixing glass and add the Angostura bitters. Muddle them together until the sugar is mostly dissolved.

Pour in the brandy over the muddled sugar mixture.

Gently stir the mixture to combine.

Using a strainer, pour the brandy mixture evenly into each chilled flute.

Carefully top each glass with the Champagne.

Twist a piece of lemon peel over each cocktail and drop it in as a garnish.

Serve immediately while it's bubbly and fresh.