Graham wafer lemon bars have the perfect balance of sweet and tart. This lemon square recipe was passed down from my Grandma, who is is in her mid-90's now and had 10 little mouths to feed (so you know it's gonna be good!).
Line a large cookie sheet with wax paper. Fill it with one layer of graham wafers. I use around 14 ½ sheets, broken into 4 pieces each along the dotted lines. (The amount you use will depend on the size of your sheet pan.)
In a medium bowl, whisk the sweetened condensed milk with the lemon zest and lemon juice. Stir well.
1 can sweetened condensed milk, 3 lemons
Spread the mixture evenly over top of the graham wafer layer. Add another layer of wafers on top. (They don't need to overlap exactly.)
In a large bowl, mix together the icing sugar, melted butter, vanilla and lemon juice. Add the warm water, a small amount at a time. (You may need to add more or less water to achieve a thick but spreadable consistency.) Add the lemon zest and mix well.
Spread the frosting on top of the wafers. You can use an angled frosting spatula dipped in warm water to help with spreading.
Refrigerate for at least 1 hour. Slice into bars and serve!
Notes
Store in an airtight container in the fridge for up to 1 week.
Freezing makes the bars soggy once thawed.
I use Honey Maid graham crackers because they are the perfect size for this recipe. You can break each cracker sheet into 4 pieces along the dotted lines. This allows for the smaller serving size. If you buy a different brand, the sheets might be a lot smaller and there will be no need for breaking them into smaller pieces (the bars will end up being a different size from my bars but that's okay).
You will need more than 1 box of graham crackers for this recipe.
I recommend using a zester for the lemons because I find it easier to use. With the zester, you can get really fine bits that are easier to mix into recipes, while a peeler usually takes bigger pieces.
To make them more aesthetic, you can top the lemon bars with some lemon zest or a few edible flowers right after frosting them.