Put the butter in a bowl and knead the flour, sugar, oats and chopped hazelnuts into the butter.
Add the salt and a little water to bring the dough together and make it pliable.
Put the dough in the fridge for approx. 30 minutes so it can rest and become easy to work with.
Rinse the blackberries in cold water and put them in a bowl.
Roll out the dough onto a sheet of baking paper – very thin and with a diameter of about 26–28 cm.
Place the blackberries in the middle of the dough and sprinkle with finely grated lemon zest, finely chopped thyme and cane sugar.
Fold the edges up over the filling so that the edges hold it all together – a bit.
Put the galette in the oven and bake it for 20–25 mins at 170 degrees Celsius until it is nicely golden on top and the crust has become crisp.
Stir the contents of the vanilla bean, the honey and the juice from the lemon into the yoghurt to make vanilla cream.
Take the galette out of the oven and let it cool a bit, sprinkle with icing sugar, and serve with the vanilla cream.