For the buttermilk crust:

1. In a food processor, combine flour, salt and sugar and pulse to combine. Scatter the diced butter over and pulse about 10 times, until slightly mixed. Pour in the cold buttermilk* and pulse until the dough is sticky and comes together.
2. Pour the dough out onto a sheet of cling film, flatten into a thick disc, then wrap in cling film. Place in the refrigerator for about 1 hour.

For the peach filling:

1. In a medium mixing bowl, combine the peaches, honey, and vanilla, until peaches are well coated.
2. Remove the dough from refrigerator, place over a sheet of parchment paper and roll out into a 10-inch (25 cm) circle .
3. Sprinkle the almond meal over the dough, leaving about 2 inches (5 cm) around the border. Arrange the peaches on top of the almond meal, then fold the edges of the dough in over the fruit, pleating the edges as you work your way around the fruit to form a free-form tart that is roughly 9 inches (23 cm) in diameter.
4. While still on the parchment, place the galette onto a baking sheet and place into the freezer for 30 minutes to an hour. This will help the galette maintain its shape during baking.
5. Once chilled, preheat the oven to 400°F (200°C).

For brunching:

1. Prepare the egg wash by mixing one beaten egg with one tablespoon of water, and brush over the edges. Sprinkle the edges with raw sugar, and sprinkle slivered almonds over.
2. Bake the galette for about 30-35 minutes or until golden brown and the juices are bubbling. Serve lukewarm with a side of whipped cream or vanilla ice cream.