Preheat the oven to 400? (200? or gas mark 6), and have a sheet pan lined with parchment paper nearby.
Spread a few tablespoons (46g) of the rinsed black-eyed peas on the prepared baking sheet, drizzle with olive oil and sprinkle with salt. Chop the top off the garlic head to reveal the cloves, sprinkle it with olive oil and salt and wrap it in the aluminum foil. place it on the baking sheet with the black-eyed peas, and roast in the oven for 25 to 30 minutes, or until the peas are crispy.
Remove the pan from the oven, unwrap the garlic and squeeze the cloves out into a food processor, discarding the skins. To the garlic, add the rest of the canned black-eyed peas, reserving the roasted ones for the top, the 1/4 cup (60 ml) of olive oil, tahini paste, lemon juice, water, cumin and salt to taste. Puree until smooth. Transfer to a serving bowl, and top with the crispy black-eyed peas and drizzle lightly with olive oil.