Preheat oven to 400°F (200°C), line a baking sheet with baking paper and set aside.
Combine flour, baking powder, salt, dried thyme and sage in a large bowl. Stir with a fork so that the herbs are evenly distributed through the flour.
Take 7 tablespoons (100g) of butter (store 1 tablespoon for later) and slice it into small cubes. Add butter to the flour mixture and mix it in with your hands by squeezing each butter cube with your fingers. Keep doing this until the mixture looks crumbly in texture.
Add the grated parmesan and stir to combine.
Fold in sour cream, either with a spatula or your hands and roughly shape a blob of dough. Scrape it out onto a floured surface and shape it into a small rectangle.
Roll it out to about 1/2 inch (1-cm) thick. Fold the ends to meet in the middle, then fold the dough again at the seam. However you do this, you want 4 layers of dough. Pat it down with your hand or a rolling pin, so you get a rectangle again, at least 1 inch (2.5 cm) thick. Slice it into 8 pieces.
Place biscuits on the baking sheet, leaving some space around each one. Melt the remaining 1 tablespoon of butter and brush the biscuits with it. Sprinkle with freshly grated pepper and bake in the middle of the oven for about 15 minutes. Just until the biscuits are deep golden brown on top.
Remove from the oven, allow to cool slightly and enjoy.