Line both muffin pans with cupcake liners before you start mixing anything. I always check that I have space cleared in my fridge first, since both pans need to fit in there together later. This small step saves a lot of scrambling once your filling is ready to go.

Stir the graham cracker crumbs, brown sugar, and melted butter together in a bowl until it looks like damp sand. Spoon about a tablespoon and a half into each liner, then press it down firmly with the back of a spoon. A tightly packed crust is what keeps these from crumbling apart later.

I like giving the crusts a quick 5 minutes in a 350°F oven just to firm them up, though this step isn't required since the recipe is technically no-bake. If you skip it, the crust will still taste great, just slightly more delicate. Let baked crusts cool for about 10 minutes before adding filling.

Beat the cold heavy cream on medium-high speed until stiff peaks form, which takes about 3 minutes. This is the ingredient that gives the filling its light, mousse-like structure, so don't rush or skip it. Set the whipped cream aside while you prepare the cream cheese mixture.

Beat the softened cream cheese and granulated sugar together until completely smooth, scraping the bowl as needed. Mix in the sour cream, lemon juice, and vanilla extract until there are no lumps left. Gently fold in the whipped cream using a spatula, turning slowly so you don't lose all that airiness.

Spoon or pipe about 2 tablespoons of filling over each crust, then smooth the tops flat with the back of a spoon. I personally prefer piping since it's quicker and keeps things neater. A simple zip-top bag with the corner snipped off works just as well if you don't own a piping bag.

Refrigerate the cups for at least 3 hours, or up to two days, covering them if they'll sit longer than a few hours. I never try to rush this in the freezer, since the crust freezes faster than the filling sets. Patience here really is what makes the texture perfect.