Warm the milk, place in a small bowl, sprinkle over the yeast and allow to activate.
Place the flour into the bowl of a stand mixer fitted with the paddle attachment. Add the yeast mixture, water, olive oil and salt and mix until well combined.
Oil a large bowl, place the dough inside and coat well with the oil. Cover the bowl with clingfilm and place in the refrigerator overnight.
The next day, line a baking tray with baking paper. Place the dough on a lightly floured bench. Form into a 20cmx20cm square, cut in half and form each into loaves roughly 10cmx 20cm. Place onto the prepared tray, gently rub with olive oil and cover with clingfilm. Allow to prove for 2 hours.
Meanwhile, toss the potatoes in olive oil and roast in a oven preheated to 200C for 15 minutes. Set aside.
Increase the oven to its highest setting and place a small tray of water on the base of the oven. Press deep indents into the dough with your fingertips and place roasted potatoes in the holes. Sprinkle each loaf with sea salt and fennel seeds and press in rosemary leaves. Drizzle with olive oil and place into the hot oven to bake for 20 minutes.
Serve bread warm or at room temperature with pesto.