Cut radishes and zucchini into tiny matchsticks with a mandoline. If you don’t have a mandoline, you can use a peeler to peel thick ribbons down the long side of the zucchini. Stack the ribbons and cut them crosswise into thin matchsticks. Cut the radishes into a similar shape by hand. Toss radishes and zucchini together. Squeeze the juice of half a lime over the radish and season with salt to taste. Add more lime juice if desired. Set aside.
Over a hot grill or an open gas-stove flame char the ears of corn until well-blackened but not completely burnt. If you’re using the burner method, you’ll probably, quickly, notice that corn likes to pop and snap, occasionally spraying you with splats of corn. It’s a little scary, which is I why I suggest you remove anyone small and easily harmed before you begin. However, I found the charred corn flavor to be completely worth the scare and hope you do too.
Remove cobs from heat, and when cool enough to handle, shave off kernels using a large knife and reserve.
Heat a large sauté pan over medium heat. Melt the butter and oil together and once hot, add the onion. Cook the onion for about 5 minutes, until softened. Add the garlic and cook another minute. Add the beans and sauté until hot, about three to five minutes. Turn heat to high, add the charred kernels of corn to the mixture, and toss to combine until heated through. Squeeze the juice of one lime over the corn mixture, and use the juice to scrape up any stuck bits. Season the corn mixture with salt and chili powder. Stir in chopped herbs.
Heat your tortillas by placing them one at a time directly on a gas stove burner, using tongs to flip them after a minute or starting to brown and blister.
Fill each taco with a few small spoonfuls of the corn mixture and slaw. Top with a spoonful of crumbled cheese. Serve with an extra lime wedge on the side, and whatever fixings you like (sour cream, avocado wedges, etc. See above).