Thanks to @nisima's suggestion (thanks!) I came across mini waffles by Marioinex and a much larger version called waffle blocks by Little Tikes.

The former comes closest to the #constructionToys I am looking for, but I still don't think it's the exact same one.
Most notable the shape of the centre hole does not match my memory of being in the shape of a plus-sign.

#MiniWaffle #WaffleBlocks #Marioinex #LittleTikes #MiniWaffleBlocks