To make the herb oil: Create an ice bath by combining 4 cups ice and 4 cups water in a large bowl and set aside. Fill a medium saucepan with water, bring to a boil, and add the herbs. Blanch for 20 seconds. They will start to wilt and darken in color. Using a slotted spoon or spider strainer, remove the herbs and quickly transfer to the ice bath, then remove from the ice bath and squeeze out as much water as possible by wrapping in a cloth or paper towel. Combine herbs and grapeseed oil in a blender and process until dark green in color. Using a fine mesh strainer, strain the oil in a jar and store in a refrigerator until ready to use, or within 3 days.
To make a tartine: Toast the sourdough in a toaster, under a broiler, or in a cast-iron skillet set over medium-high heat. Rub a raw garlic clove into the bread to release the aroma. Whip the ricotta in a blender or food processor with a drizzle of olive oil to make it extra fluffy and smooth. Once smooth and a desired texture, add the whipped ricotta to a pastry bag and pipe onto the toasted sourdough. Top the sourdough with the herb oil and garnish with lemon zest, sea salt, and extra herbs if desired. Repeat with remaining slices and serve.