1. For the leeks, trim the roots if overly long, but leave enough to keep bases intact. Slice off most of the green tops. Slice leeks in half lengthwise. Rinse under running water, gently fanning layers to wash out any trapped grit. Leeks love sandy soil, so make sure to give them a good wash, as to avoid grainy tasting leeks!
2. Heat a sauté or frying pan large enough to hold leeks in a single layer over a medium flame. Add oil and butter and swirl together.
3. Arrange leeks in pan, cut side down, and sauté, turning occasionally with tongs and spatula, until lightly browned, about 5 minutes. Handle leeks gently when turning to keep as intact as possible.
4. Add stock, water and 1 tablespoon parsley to pan. Bring to a simmer, reduce heat and cover pan, cooking leeks until tender, about 10 minutes. Arrange leeks on a serving platter, cut side up.
5. Add lemon juice and mustard to pan, whisking to combine. Season vinaigrette with salt and pepper. Pour vinaigrette over leeks and sprinkle with remaining parsley. Serve immediately. Enjoy!

Enjoy as a side with grilled stake! Top with some parmesan curls or capers to add a bit more of a salty taste!