To a blender, add avocados, roasted serrano chile, and lime juice. Blend until smooth (add water as needed to blend smoothly). Season to taste with salt and pepper.: The moment you start blending you'll notice the avocados turn into a glossy, pale green emulsion that smells fresh from the lime juice and fragrant from the charred serrano chile . Use short pulses at first, then blend steadily, adding a tablespoon of reserved cup water if necessary to keep the blades moving. This silky sauce should coat the back of a spoon, showing it is thick but pourable. The reason this technique matters is the avocado's texture: overblending can heat it and change the flavor, and underblending leaves lumps. A common mistake is adding too much water at once, which thins the sauce; avoid that by adding liquid gradually. If the sauce tastes flat, a pinch more salt and a squeeze more lime juice will brighten it instantly.
In a medium saucepan bring 4 cups water to boil. Add tomatoes and boil until cooked through, about 5 minutes. Reserving 1 cup of cooking water, remove tomatoes and transfer to a blender.: As the Roma tomatoes hit the boiling water you'll hear a gentle pop and see their skins soften and darken, indicating they are breaking down and releasing juices. Boiling concentrates their sweetness and mellows the raw tang, which is crucial for a balanced tinga sauce. When you lift them out, the reserved tomato water will be aromatic and slightly cloudy, perfect for adjusting the sauce consistency. If you skip reserving the water you might have trouble achieving the ideal texture later. A tip: do not overboil the tomatoes, or they will become mealy and lose brightness.
To the blender with the tomatoes, add 1 cup water (reserved from boiling tomatoes if desired), onion, garlic, and chipotle chiles in adobo. Blend until smooth, about 2 minutes. Season to taste with salt and pepper.: When you blend these ingredients the sauce will deepen in color to a smoky reddish brown while emitting a warm, smoky aroma from the chipotle chiles in adobo . The blended onion and garlic round out the flavor and knit the sauce together. Blending thoroughly ensures no fibrous bits remain, giving a luxurious mouthfeel. This technique is important because a smooth sauce clings better to the cauliflower . Avoid the mistake of adding too many chipotles at once; their heat can escalate quickly, so taste and adjust in small increments.
In a Dutch oven or large saucepan over medium-high heat, add sauce and cauliflower florets and bring to boil. Reduce heat and simmer until florets are tender, about 10 to 15 minutes. Season to taste with salt and pepper and keep warm.: The first few minutes after adding the sauce you'll hear a steady simmer and see the sauce bubble gently around the cauliflower , which helps the florets absorb smoky tomato flavors. As they soften the aroma fills the kitchen with a warm, roasted tomato and chipotle scent. Simmering until tender ensures each piece is fork tender yet intact, allowing a satisfying bite. This step matters because cooking the cauliflower in the sauce lets it soak up flavor rather than just being tossed with it. A common error is boiling too hard, which can break the florets apart; keep the heat to a gentle simmer for best results.
In a large skillet over medium-high heat, add about 1/2 inch vegetable oil and heat to 350 degrees. Add one tortilla to the skillet and cook until it is blistering but still soft, 10 to 15 seconds. Using tongs, turn tortilla over and then immediately fold to form a taco shell.: When the oil is at the right temperature you'll see small bubbles form around the tortilla edge and hear a faint sizzle as it blisters, an instant sign that the corn is toasting and becoming pliable. Folding it quickly while hot locks the shape and creates a pocket for fillings. Getting the timing right matters, because a too-cool pan yields greasy, limp tortillas, while oil that is too hot will burn them in seconds. A typical mistake is overcrowding the pan, which drops the oil temperature and prevents consistent blistering.
Once the tortilla is holding its shape, turn until crisp and golden all over, 15 to 30 seconds longer. Transfer to a plate loosely tented with aluminum foil to keep warm while repeating with remaining tortillas.: As you continue frying, the folded shells will begin to take on an even golden color and a satisfying crunch that contrasts nicely with the soft filling. Transfer them to a warm plate covered loosely with foil to retain crispness without steaming them. Keeping the shells warm is important so the filling does not cool the entire taco. Avoid stacking the shells too tightly or they will lose crispness from trapped steam. If you notice oil pooling on the plate, line it with paper towels to absorb excess oil.
To assemble the tacos, line the bottom of a shell with lettuce. Top with cauliflower tinga, sliced radishes, avocado sauce, and fresh mint.: As you build each taco you will appreciate the layers: the crisp shredded lettuce first creates a cool base, the warm cauliflower adds saucy, smoky richness, and the thin radishes provide a peppery crunch. Dollop the creamy avocado sauce and finish with chopped mint for a bright contrast. The order matters because the lettuce protects the shell from sogginess and the cream balances the heat. A common mistake is overfilling the shell, which makes the taco hard to handle; keep portions moderate for the best eating experience.