Broccoli Feta Soup

Heat oven to 450ºF with racks set in upper middle and lower middle positions.
Toss 2 peeled and diced potatoes potatoes and 1 onion cut into wedges with 2 tablespoon oil and ½ teaspoon salt on a sheet pan. Trim top ¼-inch off top of garlic head; place garlic, cut side down, on sheet pan.
Transfer to upper-middle rack of oven and roast 20 minutes.
Remove sheet pan from oven and clear a small space in center of sheet. Break 1 ounce of feta off of block and set aside for garnish. Place remaining 7-ounce block of feta in center of sheet pan. Return to upper middle rack and roast until potatoes are tender and onions and feta start to brown, 20 minutes
On a second sheet pan, toss 2 heads of broccoli cut into florets with 2 tablespoons oil and ½ teaspoon salt. Arrange in an even layer then cover tightly with foil and place on lower-middle rack. Roast until tender, about 20 minutes (while potatoes roast as well).
Add 5 ounces spinach, 4 cups broth, 1 tablespoon Dijon and ¼ cup dill to a high-powered blender. Blend on high until smooth.
Remove roasted vegetables from oven and allow to cool slightly, just until cool enough to handle. Scrape vegetables and feta into blender then squeeze roasted garlic cloves into blender; blend on high until smooth (depending on size of blender, you may need to do this in batches). Season to taste with salt and pepper.
Pour into serving bowls and crumble reserved feta over top.