Method

• 1.
  For the tarragon-mustard sauce, place the yolks, lemon juice and both mustards in a small food processor and whiz to combine. With motor running, gradually add the grapeseed oil in a thin steady stream until emulsified and combined. Transfer to a medium bowl, add the remaining ingredients, season to taste and stir to combine. Set aside.
• 2.
  Half fill a large, high-sided, heavy- based saucepan with oil over high heat. Heat the oil to 160°C (a cube of bread will turn golden in 3 minutes when the oil is hot enough). Make sure the pan is big enough to allow the oil to rise slightly and bubble when deep-frying.
• 3.
  Meanwhile, cut potatoes into long rough rectangles. Make sure you keep and use the misshapen rounded wedges, too! Carefully add the chips to oil and being mindful of the splattering oil, spread evenly around the pan. Stir carefully to ensure all potatoes have been coated in oil and stir gently so the potatoes settle. Don’t worry if the potatoes are not totally submerged, as long as it’s at the three-quarter level. Fry potatoes, gently stirring occasionally, until the oil temperature returns to 160°C (this will take approximately 15-25 minutes).
• 4.
  Add garlic and continue to cook for a further 4-5 minutes. If they look too straight with defined edges this is when you can gently break up a few of the chips to expose a little more surface area for ultimate crispy bits!
• 5.
  Increase the heat to 170°C and fry, stirring gently to prevent potatoes from sticking, for a further 8-15 minutes until golden and crisp. Using a large perforated spoon, remove chips from oil and drain on paper towel. Season to taste. Scatter with extra tarragon leaves and chopped chives. Serve with tarragon-mustard sauce alongside.