Place the egg yolk in a large mixing bowl. Add the apple cider vinegar and lemon juice. Whisk vigorously until creamy and pale for about 2 minutes. Next add the smoked paprika and a pinch of salt, whisking vigorously for another minute. The mixture should be starting to thicken. Now, slowly begin to add the olive oil to the mixture, adding 1 tablespoon at a time, while continuously whisking fast to incorporate the oil. Next whisk in the sriracha, and then the salt and pepper to taste. The aioli will be thick and creamy in texture. Store in the fridge until ready to use.
Preheat the oven to 375 degrees F.
In a bowl add the diced avocado, mascarpone cheese, dijon mustard, lemon juice, cilantro, green onions, crab meat, machego cheese and about 2 ounces of crumbled blue cheese. Mash everything together with a spoon and season lightly with salt and pepper.
Grab your piquillo peppers, and begin stuffing about 1-2 tablespoons of the filling in each pepper. Place the stuffed peppers on a lightly greased baking sheet. Once all the peppers have been filled, place them in the oven and bake for 15-20 minutes or until the cheese is oozing out.
Remove the peppers from the oven and turn the oven to broil. Place the ciabatta on a greased baking sheet and drizzle with olive oil, salt and pepper. Place under the broiler for 1-2 minutes or until toasted (watch carefully). Remove and sprinkle each piece of toast with blue cheese. Place back in the oven for about 30 seconds. Remove from the oven.
Serve the peppers atop the ciabatta toast and drizzle with aioli. Enjoy warm!
*The aioli can be made about 3 days in advance. *The peppers can be stuffed and stored in the fridge 1 day in advance, prepare as directed.