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1
Preheat the oven to 450.
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2
Spread 1/4 inch of rock salt in a pie plate.
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3
Arrange the potatoes on top of the salt, cover with foil and bake for about 40 minutes, until they are tender.
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4
When the potatoes are cool enough to handle, peel and pass them through a ricer into a bowl.
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5
Add the sour cream, egg, flour, salt and nutmeg to the potatoes and stir gently until incorporated.
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6
Transfer the potato mixture to a resealable plastic bag and cut 1/2 inch off one of the corners.
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7
Line a baking sheet with parchment paper and dust with flour.
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8
Pipe 1-inch gnocchi onto the baking sheet and cover with plastic wrap.
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9
In a small bowl, blend the butter with the garlic and parsley and season with salt and pepper.
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10
In a small saucepan, bring the white wine to a simmer, add the snails and cook over low heat for about 5 minutes.
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11
In a large, deep skillet, heat the olive oil.
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12
Add the oyster mushrooms and season with salt and pepper.
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13
Cover and cook over moderately high heat, stirring a few times, until starting to brown, about 3 minutes.
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14
Uncover and cook, stirring, until the mushrooms are browned and tender, about 4 minutes longer.
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15
Add the snails and 1/2 cup of the wine they were in and bring to a simmer.
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16
Stir in the garlic butter and sherry vinegar and remove from the heat.
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17
In a large pot of boiling salted water, cook half of the gnocchi until they float to the surface.
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18
Using a slotted spoon, transfer the gnocchi to the sauce.
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19
Repeat with the remaining gnocchi, gently folding them all into the sauce.
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20
Transfer the gnocchi to bowls.
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21
Sprinkle with the Parmigiano-Reggiano cheese and watercress and serve.
