Pickle jalapeño and cilantro:

Combine 2 tbsp white wine vinegar, 1/2 tsp organic sugar, and 1/2 tsp kosher salt in a small bowl; whisk until sugar dissolves. Add the thinly sliced jalapeño and 2 tbsp minced cilantro, stirring to coat. Let sit to pickle.

Massage onion with lime:

Place the thinly sliced red onion in a large mixing bowl with the zest and juice of 1 lime and a generous pinch of salt. Massage with your hands until the onion softens, then set aside.

Crack and salt cucumber:

Slice the English cucumber in half lengthwise, place cut side down, and hit with the flat side of a knife to crack. Cut diagonally into 1-inch pieces. Transfer to a bowl, sprinkle with a generous pinch of salt, toss, and allow to rest for at least 10 minutes. Squeeze out excess water by hand and discard the liquid.

Toast garlic in oil:

While the cucumber rests, heat 2 tbsp olive oil in a small saucepan over medium-low heat. Add the 4 crushed garlic cloves and cook, stirring occasionally, until golden, about 2-3 minutes.

Blend dressing until smooth:

In a blender, combine the garlic-oil mixture, roughly chopped jalapeño, zest and juice of the second lime, 1 tbsp white wine vinegar, 2 tsp agave syrup, 1 tsp yellow miso paste, 1/3 cup roughly chopped cilantro, and a pinch of salt. Blend on high until smooth.

Mix bean salad with dressing:

To the bowl with the onions, add the drained chickpeas, cannellini beans, drained cucumber, and the remaining 1/3 cup cilantro. Pour the dressing over and mix to combine.

Assemble tostadas with avocado:

Just before serving, mash the avocados in a bowl and season with a pinch of salt. Spread the mash onto each tostada, top with a generous spoonful of bean salad, and garnish with a few slices of pickled jalapeño.