Line a 9 x 13 inch baking pan with a silicone mat. You can also use tinfoil. If using tinfoil, spray with non-stick spray.
Preheat oven to 350 degrees.
Arrange the crackers in lines on the baking sheet.
Add butter, brown sugar and vanilla to a saucepan. Heat over medium high heat until simmering. Let it simmer for 5 minutes.
Pour the toffee over the crackers. Spread it evenly with an offset spatula.
Bake the toffee covered crackers for 5 minutes in the oven.
Remove from the oven and sprinkle the chopped dark chocolate over the crackers.
Return to the oven and bake for 3-5 minutes, or until all the chocolate is melted.
Spread the chocolate evenly across the crackers with an offset spatula.
Once the chocolate is spread, place in the fridge for 30 minutes, or until the chocolate and toffee are hardened.
Once the chocolate and toffee are hardened, add the white chocolate to a microwave safe bowl. Microwave the white chocolate in 30 second intervals, stirring after each, until it is completely melted.
Add the peppermint extract to the melted white chocolate and mix until combined.
Pour the melted white chocolate over the hardened dark chocolate and spread it evenly with an offset spatula. (Work quickly and try not to spread the chocolate around too much because the dark chocolate might start to melt into the white chocolate.)
Sprinkle the crushed candy canes over the white chocolate while it's still melted.
Return the baking sheet to the fridge and chill it for 30 minutes, or until the white chocolate is hardened.
Once everything is set, break the bark apart and serve!
Store leftovers in a bag or airtight container for up to 1 week in the fridge or 2 weeks in the freezer.