mushroom stock Place porcini mushrooms in a medium bowl and cover with 1 cup boiling water; let sit 30 minutes. Line a fine-mesh sieve with 2 layers of paper towel and set over another medium bowl; pour mushroom mixture through (towels will catch any grit from mushrooms). Set aside porcini mushrooms and soaking liquid.
Heat oil in a large saucepan over medium heat. Cook onion, carrot, and celery, stirring occasionally, until softened, 5–7 minutes. Add crimini mushrooms, parsley, thyme, peppercorns, salt, reserved porcini mushrooms and their soaking liquid, and 6 cups cold water. Bring to a boil, reduce heat, and simmer 30 minutes.
Strain stock into a clean saucepan and keep warm over low heat (you should have about 6 cups).
DO AHEAD: Stock can be made 4 days ahead. Cover and chill. Reheat before using.
Paella and assembly 6 tablespoons olive oil, divided 1½ pounds crimini mushrooms, quartered Kosher salt and freshly ground black pepper 1 large onion, very finely chopped ½ red bell pepper, very finely chopped ½ poblano chile, seeds removed, very finely chopped 4 cloves garlic crushed, chopped to a paste 1½ cups short-grain Spanish rice (such as Bomba)
1 cup dry white wine 1 teaspoon chopped fresh thyme, plus more for serving 1 bunch small kale, ribs and stems removed, leaves coarsely chopped (about 8 cups)
4 large eggs ¼ cup chopped fresh flat-leaf parsley Calabrian Chile Oil (click for recipe)
Preheat oven to 425°. Heat 2 Tbsp. oil in a 12" paella pan or skillet over medium-high heat. Cook mushrooms, tossing occasionally, until they release their liquid, about 4 minutes. Continue to cook until liquid evaporates and mushrooms are golden brown and tender, 5–7 minutes longer; season with salt and pepper and transfer to a plate.
Add 2 Tbsp. oil to pan and cook onion, bell pepper, and poblano chile, stirring often, until soft, about 3 minutes. Add garlic and cook, stirring, until fragrant, about 30 seconds; season with salt and pepper.
Add rice and cook, stirring constantly, until rice is translucent, about 3 minutes. Add wine and cook, stirring, until completely evaporated, about 2 minutes. Return mushrooms to pan, stir in 1 tsp. thyme, and add mushroom stock just to cover rice; season with salt and pepper. Cook, without stirring, adding broth as needed to keep rice moist while cooking, until rice is al dente and all liquid is absorbed, 15–20 ...