Seal mixture in a jar and store in a cool, dark place, stirring once a day for 4 to 5 days, or until very aromatic and beginning to ferment. When ready, return to food processor with 1/3 cup plus 1 Tbsp. rice vinegar and 1 Tbsp. cornstarch. Pulse until smooth as possible. Strain through a fine sieve over a pot, vigorously whisking and pressing on it to extract as much liquid as possible. Over medium-high heat, bring sriracha to a simmer, and reduce a few minutes until desired consistency.