If you want to prepare this dish in advance, assemble it and leave to cool, then reheat in the oven
at 200C/fan 180/gas 6 for 15-20 mins until the crumbs are browned.
Trim the stalks from the aubergines, then cut each into 6 slices
lengthwise. Lay them in one layer on a grill pan and lightly brush
with oil and a little seasoning. Grill until lightly browned, turn them
over, brush with oil again, then grill until browned and tender.
Meanwhile, heat the remaining oil in a non-stick pan, add the onion
and gently fry until softened. Add the tomatoes and simmer for 5 mins.
When the aubergines are cool, spread half the slices with a little soft
cheese and cover with the remaining slices to make sandwiches.
Spread half the sauce over a shallow ovenproof dish. Arrange the
aubergine sandwiches, overlapping, over the top and pour over the
remaining sauce. Sprinkle over the crumbs, then grill until browned.