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1
Preheat the oven to 425 degrees F.
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2
In a roasting pan, rub the 2 onions in their skins with the 2 tablespoons oil.
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3
Bake until squishy soft, turning them once, about 45 minutes.
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4
Set aside to cool completely.
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5
Peel the onions and set aside.
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6
Meanwhile, finely dice the remaining onion.
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7
Preheat a large, heavy-bottomed skillet over medium-high heat.
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8
Add the remaining 1 cup oil and heat until hot.
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9
Add the diced onion and cook, stirring occasionally, until the onions just begin to lightly brown, about 5 minutes.
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10
Lower the heat to medium-low and continue to cook, stirring occasionally, until golden brown, about 18 minutes more.
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11
Strain the onions through a sieve over a bowl.
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12
Transfer the onions to a paper towel-lined plate and spread them into a single layer.
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13
Reserve 1/4 cup of the onion oil and let it cool completely.
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14
(Reserve the remaining oil for dressings or marinades.)
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15
Puree the roasted onions in a food processor.
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16
Add the mayonnaise, sour cream, vinegar, and salt, and pulse until smooth.
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17
While the motor is running, drizzle in the 1/4 cup of the reserved onion oil until incorporated.
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18
Season with pepper and hot sauce, to taste.
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19
Transfer the onion dip to a serving bowl and stir in the scallion.
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20
Refrigerate until very thick, about 3 hours or overnight.
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21
When ready to serve top with the fried onions.
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22
Serve with chips.
