A few minutes ago, when I was looking through photos of some of my herbarium collections I saw one that immediately reminded me of this sighting. I’ve added mine (https://canberra.naturemapr.org/sightings/47048080). Mostly with these ‘flat’ fungi, identification to species (and often to genus) demands a microscopic examination of a specimen but I’m game enough to identify your sighting to species. Your subject matches mine in colour and texture. The two are not far distant from each other, since I collected the subject of my sighting between Calvary Hospital and Belconnen Way. This species is found in many places in the northern hemisphere but when it comes to Australia, I can find only 11 records of it (with yours the 12th). The other records are of herbarium specimens collected from Canberra & surrounds, near Forbes in NSW, near Hobart and near Perth. The species is undoubtedly more widespread in Australia, but is easily overlooked. I have also collected it in Black Mountain Reserve, on the small hill that is immediately north of Black Mountain. My collection points and the location of your sighting make a not-too-large triangle and I think it unlikely that the fungus occurs just at the corners of this triangle but is likely to be more widespread in the Bruce, Bruce Ridge, Black Mountain area. I’m interested in the ‘flat’ fungi, especially those with a soft consistency and I find it interesting that, here we have three sightings relatively close to each other. Otherwise, in the ACT, I have found this fungus once at Cook and once along Corin Dam Road.