1. For the potato fritters, heat up deep fryer or add enough oil to a suitably-sized heavy saucepan, and bring temperature to between 170 and 180°C.
2. In a medium-sized bowl, whisk the tempura flour with the water to a relatively runny batter. Set aside.
3. Peel and slice potatoes into rounds that are about 5mm thick.
4. Once the oil is up to temperature, dip the potato rounds into the tempura batter, then carefully slip into the hot oil. I do about five at a time. Cook for around 3 minutes. Then place on a piece of paper towel. Continue until all are done. This is the first cook. Refrigerate until required. These can be prepared a day or two ahead of time if it suits.
5. For the ranch dressing, place all the dressing ingredients, except the salt and pepper, in a suitably-sized bowl. Mix until combined, then season to taste with the salt and pepper. Refrigerate until required.
6. Heat your deep fryer or oil to around 180°C.
7. For plating and serving, cook the potato fritters in batches for a couple of minutes until golden. Drain on a piece of paper towel, then place in a bowl. Season the fritters with sea salt and some of the spice mix.
8. Top each fritter with a ribbon of the cold smoked salmon and add a dollop of the ranch dressing. Finally, dust some more spice mix over each one, then serve with a few lemon wedges for squeezing. Eat now.