Based on http://www.thekitchn.com/ with my modifications
Makes about 30 pieces of candy
to 5 matzo pieces (See Recipe Notes)
2 cup firmly packed dark brown sugar
2 cup (4 sticks) butter
1 cup chopped bittersweet chocolate or semi-sweet chocolate chips
Optional: Toppings, like chopped nuts, candied ginger, sea salt, peanut butter chips, and chocolate chips
Preheat the oven to 375°F and line a baking sheet with aluminum foil or parchment paper. For ½ recipe use a 9”x9” pan. Place the matzo in one layer on the baking sheet, breaking it when necessary to fill the pan completely.
In a large sauce pan, melt the butter and brown sugar over medium heat, stirring constantly. Once the mixture reaches a boil, continue to cook for an additional three minutes, still stirring, until thickened and just starting to pull away from the sides of the pan. Remove from heat and pour over the matzo, spreading an even layer with a heat-proof spatula.
Put the pan in the oven, then immediately turn the heat down to 350°F. Bake for 15 minutes, watching to make sure it doesn't burn. If it looks like it is starting to burn, turn heat down to 325°F. (While it is cooking, resist all urges to scrape the pan with extra pieces of matzo. You will burn yourself. Trust me.)
After 15 minutes, the toffee should have bubbled up and turned a rich golden brown. Remove from the oven and immediately sprinkle the chocolate over the pan. Let sit for five minutes, then spread the now-melted chocolate evenly over the caramel with a spatula.
You can leave it just as is, enjoying the simplicity, or sprinkle the brittle with toppings while the chocolate is still melted.
Let the brittle cool completely, then break it into smaller pieces and store in an airtight container. Rumor has it that this will last a week stored properly, but well, I've never had it last long enough to test out the theory.
When it's not Passover, you can use unsalted saltine crackers instead of matzo, but I prefer the flavor and texture of matzo.