Place the grated cucumber in a fine-mesh sieve. Use your palm and push to squeeze out as much liquid as possible; set aside.
In a small saucepan, whisk together the water and flour until smooth. Turn heat to medium and continue whisking until the mixture thickens, about 6 to 7 minutes; the mixture will resemble a roux or melted cheese. Remove from the heat.
Place the flour mixture, cashews, garlic, vinegar, oil, lemon juice, and salt and pepper, to taste, in a high-speed blender; blend for 1 minute until smooth. Pour the mixture into a bowl; stir in the grated cucumber and dill. Let the tzatziki come to room temperature, then refrigerate for at least 4 hours.
Remove from the refrigerator when ready to serve and give it a good stir.
Place chickpeas, sliced radishes, onions, and avocado in a large bowl. Season with salt and pepper. Add tzatziki and toss. Taste and adjust, adding more tzatziki, salt, or pepper if needed.
Garnish with toasted sesame seeds and herb or vegetable flowers. Enjoy!
