1. Heat the oil in a sauce pot. Add the onions and garlic. Season with salt and pepper. sauté until the onions are translucent.
2. Add the water, mustard seeds, cider vinegar and sugar to the onions and garlic. Bring to a boil. Simmer over low heat for 10 minutes or until the liquid has reduced and the mustard seeds are sticky and hold together in a clump. Season with salt and pepper. Mix thoroughly.
3. Spread the mixture in a full-size 2" hotel pan. Allow to cool. Transfer to a storage container. Cover, label, date and refrigerate for future service.
1. Peel the rutabagas. Dice into 1" squares. Place in boiling salted water. Simmer until just cooked through. Place in a colander. Allow to drain. Place on a parchment-lined sheet pan. Allow to cool.
2. Peel the celery root and carrots. Keep separate. Cook times will vary. Place in mixing bowls. Drizzle 1 Tbsp. of olive oil over each vegetable. Season to taste with salt and pepper. Place on parchment-lined sheet pans. Place in a 350°F convection oven. Cook 30 minutes or until tender. Allow to cool.
3. Trim the fennel and leeks. Slice thin. Place 1 oz. of olive oil in a heated sauté pan. Add the fennel and leeks. Season with salt and pepper. Sauté until tender. Allow to cool.
4. Place the rutabagas, celery root, carrots fennel, leeks, 2 c. of olive oil, tahini, garlic, lemon juice, turmeric and celery seed in a bowl. Mix thoroughly. In small batches place in a food processor and chop until smooth. Place in a storage container. Cover and refrigerate until needed.
To prepare à la carte:
1. Spray both sides of two pieces of bread with the olive oil spray. Grill on both sides until browned and crunchy.
2. Place ½ oz. of arugula on a serving plate. Place 4 oz. of root vegetable hummus on top of the arugula. Place 1 Tbsp. of mustard seed relish on top of the hummus. Slice the bread slices diagonally. Stack them next to the hummus.