This dessert gets a double dose of guava, in both its velvety batter and smooth jelly layer. If you can’t find guava nectar at your local supermarket, try any Asian or Latin American grocery store—you’re almost sure to hit the jackpot there. Freezing this popular Hawaiian dessert before the party made slicing it into perfect squares a cinch, although we did have to shoo away a few nosy kids (and grown-ups!) while the pieces thawed on the counter.