Bring a large pot of water to a boil. Just before blanching add a couple tablespoons of salt to the water. Plunge the greens into the water, cook a couple of minutes, then transfer immediately to a cold water bath. Drain. Squeeze out as much water as possible. Roughly chop. Set aside.
Heat a skillet with olive oil. Add the onions and/or leeks, season with salt and pepper, and saute until soft and translucent, but not browned. Set aside to cool.
In a large bowl, mix the greens, artichokes (reserve a few wedges to scatter on top), sauteed onions/leeks, scallions, feta, Parmesan, chopped dill, and lemon zest. Mix in the egg. Add a squeeze of lemon juice. Taste and season with salt and pepper.
Forming the Galette
Preheat the oven to 400 degrees (with your pizza stone, if using). Lightly flour your work surface. Roll out the dough into a large, thin circle. Place your filling in the middle, leaving a couple of inches clean around the edges. Scatter a few artichoke wedges on top. Fold in the edges so they overlap a bit. Continue all the way around, until all edges are folded in. Brush the top of the dough with egg wash. Bake on a pizza stone or baking sheet for 30 to 35 minutes until golden brown.makes 1 large galette
For galette:
Add the flours, salt, and butter to a food processor and pulse until you have fine crumbles. Add the water slowly, pulsing until the dough comes together into a ball (you may not need all the water, so add a little at a time). Try not to overwork the dough too much.
Form into a ball and flatten. Wrap in plastic wrap and place in the refrigerator for 30 minutes to an hour or even overnight.