Combine the graham cracker crumbs, melted butter, and brown sugar in a medium bowl, stirring until the mixture looks like wet sand. Firmly press this mixture into the bottom of a lined muffin tin, forming 12 individual crusts. Place in the refrigerator while you make the filling.

In a large mixing bowl, beat the softened cream cheese until it is smooth and fluffy. Add the granulated sugar and vanilla extract, beating continuously until thoroughly combined. Stir in the lemon juice, then gently fold in the whipped heavy cream until no streaks remain.

Carefully fold 1 cup of the fresh raspberries into the cream cheese mixture, letting some berries crush slightly to form colorful swirls. Set aside the remaining raspberries for topping.

Divide the cheesecake mixture among the prepared crusts by spooning or piping, filling each cup nearly to the top. Use a spatula to level the surfaces. Cover loosely and refrigerate for at least 4 hours or overnight, until fully set.

After the cheesecakes have set, carefully lift each one out of the muffin tin. Place fresh raspberries on top of each and add a small mint leaf as a garnish. Serve chilled to enjoy the best flavor and texture.