For the garlic-chipotle love: Preheat the oven to 300 degrees F.
Pour the oil into a heavy ovenproof medium saucepan and add the garlic. Cover the pot with foil, put it in the oven and cook until the garlic turns a nutty brown and is really soft (think cream cheese), about 45 minutes.
Put the garlic and the now garlic-infused oil in a food processor or blender. Add the cilantro, chipotles and sauce, salt and lime zest and puree until the mixture is very smooth.
For the chipotle-agave glaze: Combine the garlic-chipotle love, agave and lime zest and juice in a bowl and whisk until smooth.
For the mango salsa: Combine the bell peppers, red onions, mango puree, cilantro, lime juice, salt, pepper, mangos and jalapenos in a mixing bowl.
For the avocado tempura: Heat the vegetable oil in a Dutch oven until a deep-fry thermometer inserted in the oil registers 375 degrees F. Line a baking sheet with paper towels.
In a large bowl using a fork, slowly stir the tempura batter mix with the cold club soda and a pinch of salt until just combined. Add the avocado slices to the batter and toss to fully cover. Using a slotted spoon to allow excess batter to drain off, transfer the avocado slices to the oil. Fry until golden brown on all sides, 2 minutes total. Transfer to the prepared baking sheet to drain and season to taste with salt.
For the tacos: Preheat a griddle (la plancha) over medium-high heat.
Put each piece of mahi-mahi on a skewer, drizzle with vegetable oil and sprinkle with salt and pepper on both sides. Cook on the griddle, turning to brown both sides, 2 to 3 minutes per side. Brush both sides with 1/4 cup of the chipotle-agave glaze just before removing from the griddle, turning to coat.
Heat the tortillas on the griddle or in a skillet over medium heat to soften, 1 minute per side. Place on a rimmed rectangular plate. Place a ramekin of mango salsa on one side and a ramekin of lime wedges, radish and cilantro on the other side of the plate. Lay a fish skewer into each tortilla. Top each skewer with some avocado tempura, mango salsa and baby arugula. Garnish with lime wedges, cilantro and radish and serve.