Preheat the oven to 220°C. Halve the squash widthways to separate the seeded end from the fleshy end. (Reserve the fleshy end for another recipe.) Halve the seeded end and scoop out the seeds. Use the tip of a sharp knife to pierce the flesh all over, then microwave the squash on full power for eight minutes. Position them, cut sides face up, in a small roasting tin, drizzle with one teaspoon of the oil, season and roast for 20 minutes.
While cooking, heat the remaining oil in a small pan and gently fry the onions for five minutes until soft and beginning to colour. Crumble the feta into the onions and snip in half of the cress.
Pile the stuffing into the squash cavities and drizzle with the cream. Return to the oven for five minutes. Serve scattered with the remaining cress