1. Place the graham crackers in a gallon-size freezer bag and seal. Crush gently with a rolling pin until very fine crumbs. Alternatively, pulse in a food processor until very fine crumbs.
2. Put crushed crackers into a medium bowl and toss thoroughly with sugar. Stir in melted butter, stirring with a spatula until completely moistened.
3. Press into the bottom and about 1 1/2" up the sides of a 9" springform pan.
4. Chill in the freezer for at least 20 minutes.
1. In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese until completely smooth.
2. With mixer running on low, gradually pour in the condensed milk, stopping to scrape the sides of the bowl with a spatula every once in a while. Once thoroughly incorporated, add lemon juice and vanilla; mix briefly.
3. Pour filling into chilled crust.
4. Cover with plastic wrap and chill in the refrigerator for 2-3 hours, until firm.
5. Un-hinge sides of springform pan and remove.
1. While cake is chilling, make the sauce. Cook berries in a saucepan on medium-low until juicy and berries are burst, about 15 minutes. Remove from heat.
2. Place berries in a jelly bag or cheesecloth and strain over a bowl. When cool enough, squeeze out any remaining use before discarding berries. You should have about 1/2 cup of juice.
3. Place juice, sugar, and 1/4 cup water in a saute pan and cook on medium, stirring frequently until thickened. This may take anywhere between 2-5 minutes. Sauce will thicken more once cool.
4. Remove from heat and pour into a small jar or bowl. Chill until cheesecake is ready.
Eat cheesecake cold, drizzled with plenty of elderberry sauce.