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1
Preheat oven to 350u00b0F with rack in middle. Cut off and discard top of garlic head to expose cloves, then wrap head in foil and bake until very tender, about 45 minutes. Cool to warm, then peel cloves and transfer to a food processor.
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2
Stem chiles and add to processor along with vinegar, sugar, and 1 1/2 teaspoons salt. Pulse until finely chopped.
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3
Simmer chile mixture in a small saucepan, stirring, 2 minutes.
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4
Wash jars, lids, and screw bands in hot, soapy water, then rinse well. Dry screw bands. Put empty jars on a rack in a boiling-water canner or a deep 6- to 8-quart pot and add enough hot water to cover by 2 inches. Bring to a boil, covered, then boil 10 minutes. Remove canner from heat, leaving jars in water, covered. Heat lids in water to cover by 2 inches in a small saucepan until water registers 180u00b0F on an instant-read or candy thermometer (do not let boil). Remove from heat. Keep jars and lids submerged in hot water, covered, until ready to use.
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5
Carefully remove jars and lids with canning tongs, then drain jars upside down on a clean kitchen towel and quickly dry lids.
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6
Place 2 or 3 thyme sprigs in each jar and ladle sauce (while still hot) into jars, leaving 1/4 inch of space at top. Run a clean rubber spatula between sauce and sides of jars to eliminate air bubbles. Wipe off rims of filled jars with a damp clean kitchen towel, then firmly screw on lids with screw bands.
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7
Put sealed jars in canner (on rack) or pot and add enough hot water to cover by 2 inches. (If you have a jar that is partially full, do not process it. Cover it with a lid and screw band, then keep in refrigerator.) Bring to a full boil, covered, then boil, covered, 10 minutes. Transfer jars with canning tongs to a towel-lined surface to cool. Jars will seal and eventually have concave lids (you may hear a ping).
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8
After jars have cooled, 12 to 24 hours, press center of each lid to check that it's concave, then remove screw band and try to lift lid with your fingertips. If you can't, the lid has a good seal. Replace screw band. Put any jars that haven't sealed properly in the refrigerator and use them first.
