First, make your dip. In a large bowl, mash avocados together with crème fraîche, and then mix in the lemon juice, salt, and pepper. Set aside.
Make the cilantro pesto. In a food processor or blender, mix the cilantro, lemon juice, garlic, cashews, salt, cumin, and black pepper until it's a coarse puree. Then, slowly, add the olive oil until the pesto reaches the thickness you'd like.
Dish out the dip into a serving bowl. Swirl the pesto on top, or into, the dip. Slice the carrots in half lengthwise, the radishes in quarters or so, and pile them up with the charred scallions on a cutting board. Serve immediately.