Preheat the Oven:

Preheat your oven to 350°F (175°C).

Prepare the Crust:

Combine the crushed tortilla chips and melted butter in a mixing bowl. Press the mixture firmly into the bottom and up the sides of a 9-inch pie plate to form a crust.

Bake the crust in the preheated oven for about 10 minutes until it is set and beginning to brown. Remove from oven and set aside.

Cook the Filling:

In a skillet over medium heat, cook the ground beef and chopped onion until the beef is browned and the onion is translucent. Drain any excess grease.

Stir in the taco seasoning mix and water. Bring to a boil, then reduce heat and simmer for 5 minutes until thickened.

Assemble the Pie:

If using refried beans, spread them over the bottom of the baked crust.

Spoon the seasoned beef mixture over the beans.

Spread sour cream over the meat layer, and then sprinkle with shredded cheese.

Bake the Taco Pie:

Bake in the oven for about 15-20 minutes, or until the cheese is melted and bubbly.

Add Cold Toppings:

Remove the pie from the oven and immediately top with shredded lettuce, chopped tomatoes, black olives, and jalapeños, if using.

Serve:

Cut the taco pie into wedges and serve with salsa, guacamole, and additional sour cream on the side.