Not at all uncommon and nothing you really need to do. Peziza are saprobic fungi that can colonize dead, rotting wood and other organic matter, so often pop up in wood based mulches when moisture and weather conditions are right. They will disappear on their own in due course.

Thanks, I have these on some logs and stumps, didn't know the name. Not that knowing the name changes much ). I've never had it on mulch, though.

they will disappear as GG says and they will leave fertilizer in your beds. lucky you!

I know, you can barely see the stump, but it's there. It's just covered in this mushroom (which I think is the same the OP referred to, but not sure).

More mushroom fanboy photos. Snow melted (unseasonably) and this black mushroom has spread quite actively on this stump, haven't seen it before. I find it rather attractive. Looks different than the other ones I typically see on stumps but possibly a function of weather/moisture.