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1
Preheat the oven to 400F.
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2
Grease the bottom and the sides of a 13 x 9 inch pan or a rectangular 12-inch long gratin dish liberally with the butter and spread the minced garlic evenly on the bottom.
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3
Assemble the gratin: Combine the potato slices with the cream, 1 cup walnuts, 1/2 cup Parmesan cheese, Gruyere cheese, milk, nutmeg and a generous handful of salt.
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4
Mix to blend.
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5
Taste the cream for seasoning.
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6
Transfer to the prepared baking dish and spread to form an even layer.
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7
Make the crust and cook the gratin: Combine the panko with the remaining 1/2 cup walnuts and remaining 1/2 cup Parmesan cheese.
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8
Top the potatoes with the crust.
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9
Cover the dish with aluminum foil and place in the center of the oven.
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10
Bake for 20 minutes then remove foil and continue baking for an additional 25-30 minutes or until potatoes in center are fully tender when pierced with the tip of a knife.
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11
Remove from oven and let sit for 15-20 minutes.
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12
Roast the tomatoes: Arrange the tomato halves, cut side up, on a baking sheet.
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13
Season with salt and drizzle with 1 tablespoons of olive oil.
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14
Place the tray in the center of the oven and bake until the tomatoes are roasted and tender, 12-15 minutes.
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15
Set aside.
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16
Make the vinaigrette: Meanwhile, whisk together the remaining 3 tablespoons olive oil, red wine vinegar and mustard.
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17
Set aside.
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18
Finish the gratin: Serve the gratin in the dish it was cooked inches Top with the tomatoes and drizzle the top with the vinaigrette.
