FIRST, MAKE THE TOASTED ALMOND CREAM:
Preheat your oven to 375F. Place the almonds on a baking sheet and toast them until deeply brown and aromatic – about 20 minutes.
Pour the milk into a heatproof container. Heat it in the microwave or on the stove until it’s simmering. Add the almonds to the warmed milk. No need to cool the almonds before adding them. Let the steeping almonds sit at room temperature for 30 minutes, and then transfer the mixture to the refrigerator.
Steep the Toasted Almond Cream for at least 8 hours, or up to 4 days. The longer you steep, the stronger the almond flavor will be.
MAKE THE PASTRY CREAM:
Strain the almond-steeped milk into a pot. The quantity of milk that will strain out is dependent on how long you soaked the almonds. The longer you soak, the less milk will strain into the pot. (Set the soaked almonds aside – you’ll use them later). Add additional milk to the almond milk until you have a total of 240 grams. Bring the milk to a simmer.
In a medium bowl, combine the brown sugar, cornstarch, and salt. Whisk well to combine and remove any lumps. Add 1 egg to the bowl and whisk well to blend. Add the 2nd egg and whisk. Slowly stream the hot almond milk into the egg mixture, whisking constantly. Once all the milk has been added, transfer the mixture back to the pot.
Return the pot back to the stove and heat over medium heat, stirring constantly, until the mixture comes to a boil. Boil, stirring vigorously, for 1 full minute.
Remove from heat and whisk in the butter and almond extract. The pastry cream may look lumpy at this point. You can use a blender or immersion blender to smooth out the mixture. If you don’t have a blender, whisk the mixture very, very hard for 1-2 minutes.
Transfer the mixture to a storage container and store, covered, in the refrigerator for at least 4 hours.