Chill your champagne flute in the freezer for about 5 minutes to keep the drink cold and lively.
Pour the cranberry juice into a small mixing jug, adding the orange liqueur if using, and set aside.
Place 3-4 fresh cranberries in the jug and gently muddle them with a muddler or the back of a spoon, just enough to release their aroma and a little juiceābe careful not to crush them into pulp.
Remove the chilled flute from the freezer and fill it about halfway with the cranberry mixture, allowing the bright red color to shine through.
Slowly pour the chilled champagne or sparkling wine into the glass, tilting it slightly to preserve the bubbles and avoid overflow, filling it to the top.
Gently stir the drink with a bar spoon to combine the flavors without losing too many bubbles, watching as it fizzles lively and turns a soft pink hue.
Use a microplane or zest tool to create a twist of lemon zest, then gently place it on the rim or float it on top as a fragrant garnish.
Serve immediately to enjoy the crisp, bubbly, and tart brightness of your cranberry mimosa, perfect for toasts or a special brunch moment.