Step 1

For the Mille-­Feuille If you have a chamber vacuum sealer

Step 2

put an eighth sheet pan in a 12 by 15-­inch (30 by 40-­centimeter) sous vide bag

Step 3

place in the sealer chamber

Step 4

and vacuum seal. If you do not have a chamber vacuum sealer

Step 5

spray an eighth sheet pan with nonstick spray. Line the pan with two layers of plastic wrap

Step 6

extending it over the sides. Put the clarified butter in a wide 3-­quart (3-­liter) saucepot

Step 7

heat just enough to melt the butter

Step 8

and keep warm. Set a Japanese mandoline over a bowl. Slice the potatoes lengthwise into 1-­millimeter-­thick (paper-­thin) slices. Adjust the blade as necessary to be certain that the slices are solid and of even thickness. Season with the salt. Gently toss the potato slices in the pan with the clarified butter to coat. Overlap (shingle) the potato slices

Step 9

alternating between the sweet potatoes and the russet potatoes (use 2 slices of sweet potato

Step 10

then 1 slice of russet)

Step 11

in even rows to cover the bottom of the prepared sheet pan in a solid layer. Cover the potatoes with a piece of parchment paper

Step 12

set a second eighth sheet pan on top

Step 13

and press down to secure the potato slices in place. Remove the top pan and the parchment and arrange a second layer of potato slices over the first. Continue to layer the potatoes

Step 14

pressing with the parchment and sheet pan after each layer is complete. The final layer of potatoes should be level with the rim of the pan. If you have a chamber vacuum sealer

Step 15

set an immersion circulator in a water bath and heat the water to 88°C (190.4°F). Wrap the entire sheet pan twice in plastic wrap

Step 16

place it in a 12 by 15-­inch (30 by 40-­centimeter) sous vide bag

Step 17

and vacuum seal. Cook in the water bath for 1½ hours. Remove from the water bath and let rest for 15 minutes

Step 18

then submerge in an ice-­water bath until cold. Refrigerate for up to 2 days. If you do not have a chamber vacuum sealer

Step 19

preheat the oven to 300°F (150°C). Place a piece of parchment on top of the mille-­feuille and seal the pan with a piece of aluminum foil. Bake for about 1 hour

Step 20

until a cake tester inserted into the potatoes meets no resistance. Remove the foil but leave the parchment over the top. Set a second eighth sheet pan on the parchment and add weight to the pan to compress the potatoes; let stand for about 30 minutes. Transfer the potatoes with the weights to the refrigerator and refrigerate for at least 6 hours or up to 2 days.For the Compressed Asian Pear Combine the water

Step 21

sugar

Step 22

and yuzu juice in a 2-­quart (2-­liter) saucepot and warm over medium-­high heat

Step 23

stirring often

Step 24

just enough to dissolve the sugar. Pour the syrup into a bowl and season to taste with sea salt. Nestle the bowl in an ice-­water bath and let cool completely. Peel the pear and slice it just under ¼ inch (6 millimeters) thick on a Japanese mandoline. If you have a chamber vacuum sealer

Step 25

put the slices of pear and the syrup in a sous vide bag. Place in the sealer chamber and vacuum seal. The pears can be used immediately or refrigerated for up to 3 days. Punch it with a flower-­shaped cutter just over ½ inch (13 millimeters) in diameter just before using. If you do not have a chamber vacuum sealer

Step 26

punch the pear with a flower-­shaped cutter just over ½ inch (13 millimeters) in diameter and place the pieces directly in the syrup. Refrigerate in a covered container for at least 24 hours or up to 3 days.For the Caramelized Onion Jus Reduce the vinegar in a 4-­quart (4-­liter) saucepot over high heat until the pan is almost dry. Add the water

Step 27

onion essence

Step 28

mushroom essence

Step 29

dehydrated caramelized onions

Step 30

thyme

Step 31

garlic

Step 32

and bay leaf to the saucepot. Bring to a boil

Step 33

then reduce the heat and simmer for about 15 minutes. Place a dampened tea towel in a strainer set over a medium bowl. Strain the liquid into a 2-­quart (2-­liter) saucepot. Bring to a simmer and reduce to 300 grams. Strain the liquid into a blender. With the blender running on medium speed

Step 34

add the Pre-­Hy and blend to combine. Season with additional vinegar and salt to taste. Strain through a chinois into a container and cover. Refrigerate for up to 3 days.For the Creamed Arrowleaf Spinach Heat the butter in a 1-quart (1-liter) saucepot over medium-­high heat until it begins to brown. Add the leek to the saucepot and sweat over low heat until tender

Step 35

about 30 minutes. Add the cream to the saucepot and bring it to a boil. Cook

Step 36

stirring often

Step 37

until the cream mixture is very thick. It will have the consistency of a glaze and look as though it is about to split. Bring a pot of water to a boil. Blanch the spinach in the boiling water until tender

Step 38

about 3 minutes. Drain the spinach and transfer to a clean kitchen towel. Wring out any excess moisture. Place 135 grams of the spinach in the blender. Add the glazed leek and Pre-­Hy; blend until smooth

Step 39

using the tamper to help the mixture combine. Taste the creamed spinach and season with salt. Keep in a warm spot for up to 4 hours before serving or transfer to an airtight container and refrigerate for up to 2 days.To Complete Warm the caramelized onion jus and the creamed spinach in separate saucepots

Step 40

if needed. Fill a disposable piping bag with the creamed spinach and pipe it into a small squeeze bottle. Remove the mille-­feuille from the refrigerator and work with the potatoes while they are cold. Remove the weights or plastic. Lift the potatoes from the pan and place on a cutting board. Trim just enough of the mille-­feuille to smooth the edges. Cut crosswise in half

Step 41

then cut each half crosswise into 3 equal portions. Lightly crush the potato flakes in your hands and place in a shallow bowl. Put the cornstarch paste in a separate shallow bowl. Dip the bottom of each mille-­feuille in the cornstarch paste

Step 42

then dip in the potato flakes to coat. Heat the clarified butter in a large sauté pan over medium heat. Working in batches

Step 43

add the mille-­feuille to the pan

Step 44

crust-­side down

Step 45

and sauté for 2 to 3 minutes

Step 46

until the bottom is golden brown. Transfer the mille-­feuille to a cutting board

Step 47

crust-­side down

Step 48

and cut each piece into 3 equal pieces. Drain briefly on paper towels. Repeat with the remaining mille-­feuille. If the mille-­feuille have cooled before you’re ready to serve them

Step 49

transfer them to a rack set over a sheet pan and rewarm in a preheated 375°F (190°C) oven for about 6 minutes

Step 50

until warmed throughout. Arrange the mille-­feuille on the serving plates. Garnish with pieces of the Asian pear

Step 51

dots of the creamed spinach

Step 52

and chrysanthemum shoots. Spoon a few pools of the caramelized onion jus onto each plate.