In a large bowl, or the bowl of a stand mixer with dough hook attachment, add the yeast and warm water and let sit to 'bloom' for 10 minutes. It should look bubbly. Then add the butter, both types of flour and seasoning and bring together. Once a shaggy dough has formed, knead for 10 minutes by hand or 5-7 mins in the mixer (on medium).
The dough should form into a ball, but will be a little springy. Lightly oil the bowl you just used, place the dough back into it, cover with a tea towel and let rest in a warm place for 1 hour + (until doubled in size).
Cut the dough into 12 pieces. Roll into balls and then use a rolling pin to roll these into flat circles. Line a 2lb loaf tin with greaseproof paper.
Make the pesto garlic butter by combining all ingredients (make sure the butter is soft/warm).
Place about 2 tsp of this garlicky pesto mixture onto the circular disks of dough and spread over evenly with a pastry brush. Keep any mixture that's leftover
Fold the dough circles in half to form 12 semi-circles. Place these into the tin, with the filling/open side facing up (the flat side on the bottom). Line all the pieces of dough up until all are in the tin - they should be touching but don't worry if there are any gaps. Cover and let rest 30 minutes.
Preheat the oven to 200C/180C Fan/Gas 6. Brush over the remaining pesto garlic butter over the top before baking for 45-50 minutes. It should be a golden brown on top.
Let cool on a wire rack, and brush over a little melted butter for that gorgeous shine. Serve whilst still warm for best results!