In a 3-quart saucepan over medium-high heat, bring crumbs, brown sugar, butter, milk, and sugar to a boil. Reduce heat slightly and boil 5 minutes.
Meanwhile, line the bottom of 9-inch by 13-inch pan with Club crackers. Spread the boiled sugar mixture over top of crackers. Top with another layer of Club crackers.
In a small saucepan over medium heat, melt chocolate chips, butterscotch chips, and peanut butter. Stir until smooth (do not whip). Spread evenly over crackers. Cool at least 30 minutes and cut into bars.
Notes
Club crackers: Or substitute saltine crackers, graham crackers, or another squared-off cracker of your choice (the candy flavor may change with different crackers).
Butterscotch chips: If you don't love the flavor of butterscotch, add a second cup of chocolate chips instead.
Yield: Your exact yield depends on how you cut the bars. I love to cut 42 bars total, or 3 rows of 14 each (as shown in the photos).
Storage: Store these bars covered in the refrigerator (or, if you live in a cold climate, on your patio or in the garage during the chilly winter months).
Freezer: Homemade Twix Bars can be frozen for up to 3 months. Thaw in the refrigerator (or at room temperature if they are going to be enjoyed imminently).