In a small bowl, whisk together sauce ingredients, and set aside.
Combine all spice mix ingredients in a small bowl. (Extra spice mix can be kept, tightly sealed, for up to 3 months.) Rub each side of fillets with spice mix. Heat oil and butter in a large nonstick skillet over medium-high heat. Add fillets, and cook for 3-4 minutes on each side, or until fish flakes easily with a fork. Remove to a plate, and tent with foil.
Have a 16-inch square of foil ready by the stove. Heat 2 tortillas in a large, stainless steel skillet over medium-high heat for 60-90 seconds per side, until slightly blistered. When cooked, wrap them (together) in the foil. Repeat with remaining tortillas.
When tortillas are ready, place two on each plate. Divide fish, slaw and cilantro between the tortillas. Spritz with lime, and drizzle with sauce.