This comment is about another remake from a month ago. I made a Demerara syrup with a correct 2:1 ratio (constant checking over ensured that it dissolved correctly) and I made it as it is. Finally, I can understand why an Old Fashioned is so loved. The orange twist introduces a fresh fruity nose. The Bourbon then comes through, tempered by sweetness and botanicals of the bitters. Fantastic drink. I am glad to have remade the Demerara syrup and the drink itself!
Perfect as an evening sipper on a cold, wet evening watching a live concert. The slight sweetness of the bourbon works perfectly with the syrup and bitters. On my favourites.
Not really related to the cocktail, but while making the Demerara sugar syrup (2:1), the mixture clumped up completely, making it unpourable. It was like a paste, and I ended up having to make it in the glass in order to dissolve the clumped sugar. Any advice? I get the usual good results with white sugar. Cocktail's still decent though.
Update: After following your advice, I increased the water to 2 parts sugar and 1.5 parts water. The Demerara syrup worked! So thanks for that! Unfortunately, I forgot to account for the increase when remaking it, and it ended up tasting like straight Bourbon, for the most part.
It's the impurities in the sugar causing the issue but they also add to the flavour. The amount of water you will need to add will vary according to your sugar but perhaps try 2 sugar to 1.25 water or 1.5 water. (You will also need to adjust the cocktail recipe accordingly.) I use Monin's muscovado/demerara sugar as equivalent to 2:1 without the faff.