Step 1: Cut both avocados in half, remove the pits, and scoop the flesh into a bowl using a spoon.
Step 2: Using a cocktail muddler, fork, or potato masher, mash the avocado until mostly smooth but still slightly chunky. You want texture, not a purée.
Step 3: If using garlic, press both cloves through a garlic press directly into the mashed avocado. Stir to incorporate. Add the salt and taste — adjust as needed.
Step 4: Trim the green tops off the radishes and slice them as thinly as you can. A sharp knife or a mandoline gives you the cleanest, most even slices.
Step 5: Toast your bread until golden and crisp.
Step 6: Divide the mashed avocado between all four slices of toast. Top generously with the sliced radishes. Sprinkle with red pepper flakes and nutritional yeast if using. Slice each piece in half and serve immediately.
Five minutes, four servings, genuinely impressive result.