Pre heat oven to 200c.
Add 2 tsps. of olive oil and sausages to a cold oven proof skillet/pan, and fry over medium heat for 10 mins or until sausages are evenly browned - remove to a plate..
Turn heat down to medium low.
Add 2 tsps. oil & 1/2 tbsp. butter to pan, add potatoes and turn to coat evenly.
Distribute the potatoes in one even layer in the bottom of the pan, and allow to sit untouched for 3-4 mins, then loosen the potatoes from the base of the pan using a spatula then mix to redistribute back into any even layer and allow to sit untouched for another 3-4 mins to a total of 10 mins.
Add pears, fresh rosemary & sage to pan, nestling pears between potatoes to make direct contact with pan - allow to sit untouched for 2 mins - turn pears then cook for another 2 mins (see notes).
Add lemon juice, zest, 1 crushed garlic clove, 1 tbsp. butter, dried herbs if using and mix to coat evenly.
Put sausages on top of potato mixture and bake uncovered for 15 mins.
Melt remaining 1 tbsp. butter in a heatproof bowl, add remaining crushed garlic clove.
Add sourdough to butter mixture & using a pasty brush coat bread cubes in melted butter (see notes).
Remove pan from oven and sprinkle over bread cubes (see notes).
Bake uncovered for 10 mins, then serve immediately.