Spray a 9-inch square baking dish with cooking spray and line with parchment paper and set aside.
Add butter, sugar, and salt to a heavy bottomed 3 quart pot.
1 cup unsalted butter, 1 cup granulated sugar, ½ teaspoon kosher salt
Bring to a boil over medium low heat, stirring frequently to dissolve the sugar.
Once the candy is boiling, stir occasionally, slowly and evenly, until the candy has reached 290°F to 300°F, or "hard crack" on a candy thermometer.
Once the candy has reached 290°F to 300°F, remove from heat and gently stir in the vanilla extract. Pour into the prepared baking dish.
1 teaspoon vanilla extract
Let the toffee sit for 5 to 10 minutes (until it's firm enough to lift out but soft enough that you'll still be able to cut it) then lift it from the baking dish and set on a cutting board.
Use a pizza cutter to cut the toffee into 9 squares. You may need to run the pizza cutter through more than once to completely cut the toffee. Carefully separate the pieces of toffee an let cool for another 5 minutes or until firm but still warm.
While the toffee is sitting, melt the white chocolate wafers according to package directions.
15 ounces Ghirardelli White Chocolate Melting Wafers
Using tongs, dip each piece of the toffee into the melted white chocolate and then tap to let any excess drip off of the toffee. Place the toffee onto the baking sheet with the cinnamon sugar and sprinkle more cinnamon sugar over the top to completely coat the toffee. Repeat with remaining pieces of toffee.
Let toffee sit for at least 20 minutes or until the white chocolate has completely set up.
Store in an airtight container in a cool place.