Make the lemon curd. In a small saucepan over low heat, whisk together egg yolks, sugar, lemon juice, lemon zest, lemon extract, vanilla paste, and salt. Stir continuously until the mixture thickens enough to coat the back of a spoon, about 8–10 minutes. Remove from heat and whisk in cold butter one cube at a time until fully incorporated. Strain through a fine mesh strainer into a clean bowl and let cool completely.
Make the swiss meringue. Combine egg whites, sugar, and a pinch of salt in a heatproof bowl set over a pot of simmering water (double boiler). Whisk constantly until the sugar fully dissolves and the mixture reaches 160°F, about 4–5 minutes. Transfer to a stand mixer and beat on high with lemon extract and vanilla until stiff, glossy peaks form.
Make the ice cream base. Add heavy whipping cream, sweetened condensed milk, vanilla paste, lemon extract, almond extract, salt, and lemon zest to a blender. Blend until a loose foam forms and the mixture is smooth and silky. Do not over-blend.
Make the graham cracker butter. Mix crushed graham cracker crumbs with melted butter until the mixture holds together like wet sand. Set aside.
Partial freeze. Pour the lemon base into a bowl and freeze for 1 hour, until halfway frozen.
Prep your containers. Before layering, spread a thin layer of lemon curd along the inside walls of each pint container.
Layer. Start with the lemon ice cream base, then add a layer of meringue, a spoonful of lemon curd, and a sprinkle of graham cracker butter. Repeat — base, meringue, curd, graham — until the container is full.
Swirl. Using a knife or skewer, poke down into the top layer in a circular pattern, pressing gently downward to marry the layers. Don't overmix — you want ribbons, not a blend.
Top it. Finish with a dollop of meringue, a swirl of curd, and a generous pinch of graham cracker crumble to make it look as good as it tastes.
Freeze overnight. Cover and freeze for at least 8 hours.