Brush butter on the upside-down muffin pan.
Take 3x16 inches of croissant sheet and refrigerate. Divide the remaining 6x16 inches into 9 strips along the length (approximately 2/3 inch each).
Gently stretch and roll each strip around a muffin cup, ensuring no gaps. Press down to hold the strip's shape.
Cut the remaining 3x16 inches sheet into two 3x8 inches sheets. Roll each into a log, similar to a cinnamon roll, and cut into 9 circular pieces.
Place each circle on a flat surface, roll it out slightly larger than the cup's base, and place it onto the cup. Stretch to seal it with the strips placed earlier. Work one piece at a time, keeping the rest in the fridge.
Proof cups at room temperature for 2 hours until nicely puffed up. Preheat the oven to 350°F.
Brush with egg wash and place the tray in the oven. Bake for 20 minutes, then put some weight on top of the cups to flatten them (e.g., a light baking sheet). Bake for an additional 10-15 minutes with the weight.
Whisk cream cheese and sugar until combined. Add sour cream, lemon juice, vanilla, and salt, then fold in whipped heavy cream.
Heat jam with water and sugar until they form a thick syrup.
Separate each cup, fill with cheesecake batter, and top with syrup and crushed Graham crackers.
Refrigerate for 2-3 hours, then serve and enjoy these scrumptious Cheesecake Croissant Cups!