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1
Preheat the broiler.
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2
Open the hamburger buns and arrange on a baking sheet.
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3
Brush the buns all over with 1 tablespoon of the mayonnaise.
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4
Toast until golden on both sides, 1 to 2 minutes per side.
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5
Cut into very small pieces and set aside.
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6
Combine the cheese, 1/2 cup mayonnaise and a pinch of salt in a food processor and process until very smooth.
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7
Transfer to a bowl, cover and refrigerate until ready to use.
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8
Whisk together the remaining 1/2 cup mayonnaise, the ketchup and mustard together in a bowl for the sauce, cover and refrigerate until ready for use.
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9
Arrange the bacon in a large nonstick skillet (do in batches if necessary) and heat over medium heat.
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10
Cook until golden brown and crispy, 4 to 5 minutes per side.
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11
Remove, let cool slightly and chop into small pieces.
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12
Wipe out the skillet.
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13
Heat the oil in the skillet over medium-high heat.
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14
Add one-third of the onion and cook, stirring frequently, until soft and just beginning to brown, about 4 minutes.
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15
Add the ground beef, 3/4 teaspoon salt and a few grinds of pepper.
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16
Cook, stirring and breaking up into smaller pieces, until browned and cooked through, about 4 minutes.
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17
Stir in a 1/3 cup of the prepared sauce and cool the beef mixture to room temperature.
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18
Let the cheese mixture soften are room temperature, about 30 minutes, before building the dip.
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19
Layer the dip in a medium, straight-sided 3-quart clear glass trifle bowl or your favorite serving dish.
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20
Spread out the cheese mixture and then top, in even layers, with the buns, tomatoes, beef, the remaining sauce, the pickles, the remaining onions and the bacon.
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21
Wrap and refrigerate until chilled, at least 1 hour or overnight.
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22
Top with the shredded lettuce right before serving.
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23
Serve with chips for dipping.
