Add ½ cup of slivered almonds to a small baking pan. I used an 11x7 baking pan. Spread them out and place in the oven until golden brown. It will take about 16 minutes. Remove from the oven and let cool.
Blueberry Compote
In a medium saucepan, add in 1 cup of blueberries and the sugar. Place oven medium heat and smash the blueberries with the back of your wooden spoon to help get the juices flowing. I let the blueberries cook for 10 minutes.
Stir in the remaining ½ cup of fresh blueberries and place in a dish. Refrigerate until chilled.
Almond Pastry Cream
Add the almondmilk into a medium saucepan. Place over medium heat and heat until it comes to almost a boil. Steam will come off from it and it will form small bubbles. It took about 13 minutes to reach this stage for me.
While the milk is heating, prepare the thickener. Add the sugar, salt, and cornstarch in a small bowl, Whisk until combined.
Add in the 5 yolks and whisk until combined.
Once the milk has come up to almost a boil, add in ½ a cup to the egg yolk mixture, whisking constantly. Whisking constantly as you pour the mixture in and until it's combined will prevent the egg yolks from cooking and will temper them.
Add the almond paste and egg yolk mixture into the saucepan of almondmilk and whisk until combine. It should still be over medium heat. Let it heat until it thickens and covers the back of a spoon. It took about 6 minutes.
Add in the butter and whisk until it's all combined.
Strain the mixture into a clean and shallow dish. Cover the almond pastry cream with plastic wrap. Make sure the plastic wrap is sitting on top of the almond pastry cream so no skin forms.
Place in the fridge to chill. I left mine in overnight.
Crust
Preheat oven to 375 degrees.
In a food processor, add in the cold butter, powdered sugar, salt, ¼ cup slivered toasted almonds, and 2 cups of flour.
Pulse until the butter and slivered almonds are well combined into the flour.
Add in the egg and pulse until a dough ball forms.
Press the dough into a 10 inch tart pan. Using a knife, poke some holes into the bottom of the crust.
Place in the preheated oven for 15 - 20 minutes until golden brown. Remove from the oven and let cool completely.
Once completely cooled, add in all the almond pastry cream. Spread it out evenly.
Add the blueberry compote into the center of the tart.
Place the remaining ¼ cup of slivered toasted almonds around the edges of the tart.
To firm up, I placed in the freezer for about 2 hours. This allowed the tart to not fall apart so much when it was cut. Once it's completely thawed, the pastry cream will not be as firm.
Notes
To store any leftover blueberry tart, place in an air tight container and place in the refrigerator for up to 5 days.