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1
Preheat the broiler to high.
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2
Heat a deep pot over medium to medium-high heat.
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3
Add the EVOO and butter to the pot.
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4
When the butter melts, start adding the onions as you slice them.
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5
Season the onions with salt, pepper, and the rosemary.
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6
Cook the onions for 15 to 18 minutes, until tender, sweet, and caramel colored, stirring frequently.
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7
If you find that the onions are burning in spots before browning all over, add a splash of water and stir now and then, scraping the bottom of the pot.
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8
While the onions are cooking, make the topping.
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9
In a small bowl, combine the grape tomatoes, basil, grated cheese, salt, and pepper.
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10
Under the broiler or toaster oven, toast the crusty bread until golden; rub each side of the golden toast with the crushed garlic clove.
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11
Once the onions are done, add the balsamic vinegar and white wine, stirring up all the brown bits from the bottom of the pot.
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12
Add the stock and cover the pot to bring the soup up to a quick boil.
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13
Arrange 4 small, deep soup bowls or crocks on a cookie sheet.
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14
Once the soup reaches a boil, ladle it into the bowls.
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15
Float a toasted bread slice on each serving and cover each toast with a mound of the grape tomato mixture.
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16
Top with 2 slices of the mozzarella cheese.
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17
Slide the cookie sheet under the hot broiler until the cheese melts and bubbles.
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18
Work next to the stove as you slice the onions, throwing them into the pot as you go.
