If the information the Internet offers is accurate and should be taken into account, then the Hervoise is brewed at the Brasserie Vervifontaine, a small brewery next to Liege in Jalhay.
Until this mystery is solved (I think best will be to e-mail the Grain d’Orge experts and see what they advise on the above-named beer), some information on the beer: it is a strong ale like beer, slighty sparkling, brewed using the syrup de Herve which gives it a slight apple and pear taste.
A classic beer paired in the region with the plateau de Herve cheese, it was indeed a beer that pleasantly surprised us. You will ask, what about the glass, the recipe? The glass exists. However difficult to find in Brussels, it will have to be bought when visiting the brewery where this beer comes from. As for the recipe, I’ll have to pass this beer as I didn’t find anything specific to this beer. I guess a Hervoise with a plateau de Herve?