Pre-heat oven to 425. Set salmon aside to come to room temperature (20 minutes)
Preheat baking stone, or cast iron. If using cast iron pan, rub with canola or peanut oil.
Stir mustard and lemon juice together. Add herb and stir in olive oil.
Thinly slice golden Yukon potatoes, using enough to cover both sides of dish
Peel potato and slice thinly. Pat dry with paper towels. Toss in olive oil mixture.
Place parchment paper on baking dish if you don’t have baking stone or seasoned cast iron. Place potatoes on paper or stone, overlapping slightly. Place fish on top and then layer again with potatoes.
Bake at 425 for about 7-10 minutes each side. You will need to check at 7 minutes. Potatoes underneath will be crisp. At that point turn over to finish crispiness. Rest five minutes.