Skim Greek Yogurt Dip with Garlic-Rosemary Oil

Steps

1. Wash a heavy pot, whisk, thermometer, lidded jars, strainer and spoon in hot soapy water, rinse, then sanitize with boiling water and let air-dry.
2. Heat: pour the commercially pasteurized skim milk into the pot and heat over medium, stirring often, to 180°F (82°C). Hold it at 180–185°F (82–85°C) for 15 minutes, stirring so it doesn't scorch.
3. Cool: take the pot off the heat and cool the milk to 108–112°F (42–44°C), checking with the thermometer; setting the pot in a sink of cold water speeds this up, about 20 minutes.
4. Add starter: in a small clean bowl, whisk the plain yogurt with live active cultures with a ladle of the cooled milk until smooth, then stir this mixture back into the pot.
5. Incubate: pour into the jars, cover and keep at 108–112°F (42–44°C) for 6–8 hours, in an oven with only the light on or a cooler of warm water, checking with the thermometer, until set and tangy.
6. Refrigerate: move the yogurt to the refrigerator immediately and chill at 40°F (4°C) or below for at least 2 hours until cold.
7. Line the strainer with a double layer of cheesecloth or a clean towel, set over a bowl, spoon in the yogurt, cover and strain in the refrigerator for 4 hours. Expect about 800 g of thick Greek yogurt and about 1.
8. Warm the olive oil in a small clean pan over low heat, add the garlic and cook 3–4 minutes until pale golden, then stir in the rosemary off the heat and let the oil cool completely.
9. Stir the salt, black pepper, lemon zest and half the parsley into the strained yogurt, then spread it in a shallow bowl.
10. Spoon the cooled garlic-rosemary oil over the top, then scatter on the green onion and the remaining half of the parsley.
11. Serve with the carrot and celery sticks for dipping; keep leftovers covered in the refrigerator and use within 5 days.