I've never used as plantain slicer. Does not make sense since you have to get a knife dirty anyway to peel the plantain. However, my daughter gave me a tostonera, and I do use that to really flatten the tostones. BTW, use the greenest plantains you can find and flatten them as thinly as you can, so parts will really crisp. These are typically serve with just salt on them as soon as they are fried the second time, and sometimes with mojito to dip (garlic dip).
No Cuban I know would ever put chili powder on them.
C@H is mixing Mexican with Cuban again. IMHO, it is a sacrilege to put a jalapeno on a Cuban sandwich (or any Cuban dish). Here's a recipe for the garlic dip in case folks need one:
Authentic mojo is made with juice from sour oranges. It it is very acid and tart but still tastes like oranges. You can come close by mixing equal amounts of freshly squeezed orange juice with lime juice. I prefer just lemon/lime version for tostones, but you can do the orange version is you prefer.
Makes 1 cup
1/3 cup olive oil
6 to 8 cloves garlic, thinly sliced or minced
1/3 cuplime juice
1/3 cup lemon juice
1/2 tsp ground cumin (optional)
Salt and freshly ground black pepper, to taste
Heat the olive oil in a deep saucepan over medium heat. Add the garlic and cook until fragrant and lightly toasted. Don't let it brown or it will be acrid tasting, just about 30 seconds should do it.
Add the lemon and lime juices, cumin and salt and pepper. STAND BACK; the sauce may sputter. Bring to a rolling boil. Taste and correct seasoning, if needed
Cool before serving. Mojo is best when served within a couple of hours of making, but it will keep for several days, well capped in a jar or bottle, in the refrigerator.
Use with Cuban sandwiches, boiled yucca, grilled seafood and meats, fried green plantain chips, etc.
I have seen recipes for mojo using cilantro in it, but that is not traditional to Cuban Cuisine.
Enjoy.