Make the almond cream. In a food processor, pulse together sliced almonds, sugar, and salt until the nuts are finely ground. Add eggs and butter, and puree until smooth. Chill the almond cream for at least 1 hour or overnight.
Prepare the pie dough. Combine all-purpose flour with sugar, salt, butter, and cream cheese in a food processor. Pulse for 5-10 seconds or until the mixture is coarse and the butter and cream cheese are blended in. Slowly add the ice water 1 tablespoon at a time, pulsing just until the dough comes together. Alternatively, use your hands to mix the dough, adding water just until the dough starts to form. Wrap in plastic wrap and chill in the fridge while you prepare the filling.
Combine blackberries with brown sugar, cornstarch the juice and zest of ½ lemon, vanilla, and cinnamon, gently mixing to coat.
Dust a clean counter with flour and roll out the pie crust until it's a 14x12-inch rectangle. Transfer to a lined baking sheet.
Spread the almond cream in an even layer on the dough, leaving a 1-inch border. Top the almond cream with the blackberries. Fold the pastry edge up and over the blackberries to create a 1-inch border. Brush the crust with the egg yolk wash and sprinkle the sliced almonds on top.
Bake galette for 40-45 minutes or until the pastry is browned. Cover with foil if the pastry gets too browned. Remove from heat and serve warm or at room temperature.
Notes
You can prepare the almond cream filling and pie crust up to 2 days ahead of time. Store in the refrigerator until ready to use.I used sliced almonds but you can also use slivered almonds or chopped almonds.