Heat ¼” canola oil in a large, deep sauté pan or cast iron skillet over medium high heat until shimmering (a spec of flour tossed in should immediately disintegrate when oil is ready).
Meanwhile, whisk together salt, garlic powder, Old Bay, cornmeal and flour in large bowl. In a smaller bowl, whisk together egg and milk
Dip each peeled shrimp into the dry mixture, then into the egg mixture, then back into the dry mixture. Continue until all shrimp are breaded.
Fry shrimp about 2 minutes a side, flipping once, until golden brown and crispy. Remove to a wire cooling rack set over a cookie sheet to drain and cool.
While shrimp cools, toss together tomatoes, spinach arugula mix, shallot and cucumber with dressing.
To a small microwave safe bowl, add 2 tbs hot sauce, 2 tbs butter and heat in microwave, 45 seconds on high, or until butter is melted. Whisk in crushed garlic and toss fried shrimp to coat.
Divide dressed salad to 2 serving bowls, and top with shrimp, feta and sliced avocado. Drizzle with remaining hot sauce mixture, if desired.