Add white chocolate and butter to a microwave-safe, medium-sized bowl and heat in intervals of 20 seconds; stirring after each heating until completely melted and smooth.
Whisk in flour, sugar, and pumpkin pie spice until batter is smooth.
Whisk in eggs, egg yolk, pumpkin, and vanilla extract until the batter is well blended.
Using 3 (6 ounce) ramekins that have been sprayed with non-stick spray, fill each ramekin half way with cake batter. Add two caramels into each ramekin and sprinkle with sea salt (about 1/8-1/4 teaspoon per cake depending on how much salty flavor you want). Spoon remaining cake batter over each cake.
Bake cakes for 14-17 minutes and remove from oven. The cakes should be set on the outsides but still jiggly in the center.
Let cool for 2 minutes; take a knife and run along the inside of each ramekin to help release the cake.
Invert the cakes on individual plates. Dust with sea salt or powdered sugar and serve warm.
Make sure you do not overbake this cake. If you set up the center too much, you will lose the lava molten center which makes this cake so special.