4 hours before serving (or the night before) cut the strawberries in half. Place half the berries on a baking sheet, and freeze.
1 pint strawberries
Combine the orange juice and the remaining strawberries and refrigerate.
½ gallon orange juice, 1 pint strawberries
Just before serving, combine the orange juice mixture and the champagne. (For a non-alcoholic version, substitute gingerale or sparking white grape juice).
1 bottle, Lemon and lime slices
Add the frozen strawberries, which will act like ice cubes without watering down the mimosa.
1 pint strawberries
Notes
You can preserve extra strawberries by flash freezing them whole or halved on a baking sheet, then transferring them to a freezer bag for up to 1 month. (This works really well for blueberries and raspberries as well.)