What's the cocktail that has lemon ice cream, green crème de menthe, Bohemia sekt demi-sec, and mint?

It looks like you are describing a very specific and unique cocktail experience, but none of the provided cocktails in the list match exactly with those ingredients: lemon ice cream, green crème de menthe, Bohemia sekt Demi sec, and mint. However, I did find a similar cocktail called the Sgroppino / Sorbetto. It involves champagne or prosecco, lemon sorbet, cream, and vodka. While it's not an exact match, it does have the refreshing lemon element and could serve as a sophisticated alternative.

The Sgroppino, also known as Sorbetto, is a refreshing and elegant Italian cocktail that combines the crispness of champagne or prosecco with the creamy texture of lemon sorbet, enriched with a hint of cream and the clear, smooth spirit of vodka. This drink offers a delightful balance between sweetness and the lively effervescence of sparkling wine. It's traditionally served in a cocktail glass and can be an excellent choice if you enjoy lemon and bubbly elements.

If you're set on creating a cocktail with lemon ice cream, green crème de Menthe, Bohemia sekt Demi sec, and mint, you might be looking to craft your own unique concoction. Combining the fresh, tangy lemon ice cream with the herbaceous mint flavor of green crème de Menthe, elevated by the crisp bubbles of Bohemia sekt Demi sec, would certainly result in a refreshing and intriguing drink!