Hello! You are actually very close to the ideal process, but there is one critical mechanical step missing from your workflow: surface agitation to create a gelatinized starch slurry.
When you simply boil and dry a smooth-cut Yukon Gold, the exterior remains tight and flat. Without micro-fissures and released starch, the fat slides off rather than soaking into a textured exterior, leading to a soft, leathery skin instead of a blistered, shattered crust.
Here are the exact adjustments you need to make:
1. Agitate the potatoes after boiling.
Immediately after draining your parboiled potatoes, let them steam dry for a couple of minutes, then return them to the warm pot. Toss or shake them vigorously against the sides of the pot. You want the edges to fray and become coated in a thick, mashed-potato-like paste. This paste absorbs the hot cooking fat and fries into a deeply crisp shell in the oven.
2. Add baking soda to your parboiling water.
Adding about half a teaspoon of baking soda to your boiling water raises the pH (making it alkaline). Alkaline water rapidly breaks down the pectin on the potato surface, releasing significantly more starch to form that essential gelatinized coating during agitation.
3. Adjust roasting time for Yukon Golds.
Because Yukon Golds have higher moisture and lower starch content than Russets, 40 minutes at 425 degrees Fahrenheit is often just enough time to drive off internal steam, leaving little time for active frying. Aim for 50 to 60 minutes total, giving them a gentle flip halfway through once the initial crust has set and can release cleanly from the pan.
If you incorporate the alkaline parboil, rough up the exterior into a starchy paste, and roast slightly longer, you will achieve the exact blistered, glassy crust you are after.
