Marinate: Cut tempeh into thin rectangular tenders. If you're not used to the taste/texture of tempeh, cut them thinner so you'll get more of the breadcrumb crunch. Set in a deep dish and cover with buffalo sauce, tossing to evenly coat. Let marinate at least 1 hour (or up to 12) in the fridge.
Prep: Preheat oven to 375 degrees F (190 C). Shake excess sauce from the tempeh and set on a plate, reserving the buffalo sauce marinade. Place flour in one bowl, egg in another, and panko + salt and pepper in the last, with a parchment-lined baking sheet at the end. Add half of the reserved buffalo sauce to the egg and whisk.
Bread: Coat each tempeh tender lightly in flour, then egg, then bread crumbs, and set on the baking sheet.
Bake: Bake for 10 to 15 minutes, flipping halfway through, until golden brown. Brush each tender with remaining buffalo sauce, then return to the oven for 5 minutes, until slightly dry.
Serve: Serve warm with ranch dressing or bleu cheese and celery.
*Make this recipe vegan by using flax egg - Combine 1 Tbsp flax seed meal and 2.5 Tbsp water. Let thicken for 10 minutes then use in place of the egg.