60g mature pecorino or parmesan cheese, finely grated
For the garlicky toasts
1 loaf ciabatta
1 garlic clove
Measure the milk into a large bowl and stir in the bread, eggs and ricotta with a little salt and coarsely ground pepper. Don’t mix it thoroughly, a few golden streaks of egg yolk are a good thing. Set aside in a cool place.
Preheat the oven to 200°C/fan 190°C/400°F/gas mark 6. Peel and halve the squash, scoop out the seeds and cut into wedges. Toss with olive oil, season and roast in a foil-lined tin for 30 minutes. Meanwhile, cook the onion and bacon in a little oil in a large frying pan. Keep the heat gentle for five minutes until the onion softens, then turn up the flame to get the bacon sizzling. Shred half the sage and add to the pan, stir, then tip into the milk bowl.
Spread half the milk and bread out in a large, oiled gratin dish and nestle in half the squash and mozzarella. Repeat, then scatter with pecorino. Cover and chill, overnight if possible, or bake now if time is short.
Set the oven to 180°C/fan 170°C/350°F/gas mark 4 and bake the strata for 40–45 minutes, until golden and bubbling. Sizzle the remaining sage leaves in olive oil for a few seconds.
Drain on kitchen paper and scatter on top of the baked cheese.
For the garlicky toasts, grill or griddle a barrage of slender Italian bread slices - a large loaf of sourdough, ciabatta or the like should do it - until a little charred in places. Rub the hot, crisp toast surfaces with a halved garlic clove, and drizzle with a little of your best olive oil. Pile up on a board beside the strata.