Line a baking sheet with parchment paper and line up the saltine crackers in rows.
Melt the butter and brown sugar in a sauce pan over medium low heat and slowly bring the mixture to a boil. Be careful not to heat too quickly or your toffee will separate.
Boil the mixture for 2–3 minutes, stirring constantly, until thick.
Pour the thickened toffee over the saltines and spread it out evenly using a rubber spatula.
Bake the toffee covered saltines at 350 degrees for 4–5 minutes, until browned and bubbly on top.
Remove the sheet pan from the oven and sprinkle the white chocolate chips over the top of the saltine crackers.
After the chocolate sits for 5 minutes and is mostly melted, use the back of a spoon or a rubber spatula to spread it evenly across the crackers.
Top the toffee crackers with green and gold sprinkles for St. Patrick's Day.
Refrigerate or freeze the leprechaun crack until hardened, then break it into pieces using your hands or a knife.
Store leftovers in an airtight container in the refrigerator or freezer.