Slice baguette crosswise 1/2 inch thick, and toast on a rimmed baking sheet in a 375 degree oven. Meanwhile, place egg yolks, garlic, and lemon juice in a food processor. Add olive oil in a slow and steady stream, and pulse to emulsify. Add parsley, and season with salt and pepper. Pulse about 5 times to combine. Spread aioli onto toasted baguette slices.
Food safety note: The egg yolks in this recipe are not cooked.