There are so many permutations of the old fashioned, and going through them was part of the fun. I have pretty much settled on the following two as my "go to":
If I want it relatively strong:
IN A MIXING GLASS
3/4 oz of simple syrup (or a sugar cube muddled in a little water)
3 good dashes of Angostura Bitters
2 oz of rye or bourbon
A few whole ice cubes
Stir till chilled, this chills and dilutes slightly
Strain into a rocks glass over one of those huge single ice cubes (I have a mold)
Using a sharp knife, cut a piece of orange zest to use as a twist. Just the zest, none of the white part. Twist the zest over the drink and drop in. The zest is the secret. It releases the orange oils and gives it that orange smell and flavor without having to muddle a slice of orange and dilute the drink.
If I want it a little weaker:
IN A ROCKS GLASS
3/4 oz of simple syrup (or a sugar cube muddled in a little water)
3 good dashes of Angostura Bitters
2 oz of rye or bourbon
about half a glass of "cracked" ice (crack the cubes with a spoon)
Stir till chilled. Then add the rest of the cracked ice.
Using a sharp knife, cut a piece of orange zest to use as a twist. Just the zest, none of the white part. Twist the zest over the drink and drop in.
The cracked ice in this one gives you some small and some large pieces of ice. The small pieces melt quickly diluting the drink more than the first version.
I have made them muddling the orange, muddling an orange and a cherry etc etc. They are all good. I just prefer the simpler ones above.