In a dry cast iron pan over medium heat, press the dried chiles flat and toast them, turning frequently, until fragrant and pliable — about 1–2 minutes per side. You want soft and aromatic, not blistered. Do not burn them.

Add the unpeeled garlic cloves to the same dry pan. Toast, turning occasionally, until the papery skin is blackened in spots and the garlic inside feels soft when pressed, about 8–10 minutes.

Transfer toasted chiles to a heatproof bowl and cover completely with boiling water. Place a small plate on top to keep them submerged. Steep for 25 minutes.

Place tomatillos and plum tomatoes in a small saucepan with enough water to cover. Bring to a boil and simmer until tender and just starting to split, about 10 minutes.

Drain the chiles (taste the soaking water — if it's not bitter, save some for blending). Peel the roasted garlic. Add chiles, garlic, tomatillos, and tomatoes to a blender. Blend to a rough paste, adding soaking water or stock to loosen. For a looser salsa, blend more; for chunky, pulse briefly.

Season generously with salt. The flavors will be more mellow than raw salsa — that's the roasting. Taste, adjust, and transfer to a jar.