(If making the paleo version with maple syrup, skip to step 2.) Mix together 1/2 cup sugar and 1/2 cup water in a small pan over medium heat on the stove. Keep heating it and occasionally stirring until the sugar completely dissolves. You should end up with just over a half cup of simple syrup. Remove the syrup from the heat and allow it to cool.
Prepare the Lemon "Ice Cream"
Meanwhile, rinse and dry the lemons. Grate the peel of the clean lemons, obtaining only the zest for flavor. Try to avoid adding any of the white pith as it adds a bitter flavor.
Juice enough lemons to obtain around 1/2 cup of lemon juice.
Mix the cooled sugar syrup or maple syrup with the lemon juice and zest and place the mixture into the freezer for several hours until it begins to form ice crystals.
Add the egg whites to a bowl and begin to beat the egg whites until they form soft peaks.
Fold the egg whites into the cold lemon mixture until throughly combined.
Place the new mixture into the freezer for several hours more, until you are almost ready to serve your champagne sorbet. To keep large ice crystals from forming, remove the sorbet from the freezer and mix it occasionally throughout the freezing process.
Put it all together
When the time comes to serve the champagne sorbet, mix some sparkling wine with the lemon sorbet, to taste. Use just enough to make it slushy and drinkable through a straw. Some people prefer to blend the ingredients together with an immersion blender to make a more homogenous mixture. Others prefer to leave the ice cream on top, more like a "float". That, of course, is up to you.
Serve in a fluted champagne glass with a straw, optionally garnished with a sprig of mint.
Nutritional information is based on the paleo version made with maple syrup. It assumes using just over 2 Tbps. lemon sorbet with 107ml champagne per glass. Serving size is based on adding just over 2 Tbsp. of lemon sorbet with 107ml cava, 1/7th of a 750ml bottle.Non-paleo version makes for a sweeter version of the drink, but that can be adjusted by the amount of simple syrup used.Sweet sparkling wines work great, but you can also use dry or semi-dry. Use just enough to make it slushy and drinkable through a straw.For a quick, last minute lemon champagne sorbet, mix store-bought ice cream, sherbet, or sorbets with sparkling wine, to taste.