Line a rimmed baking sheet with aluminum foil and spray lightly with nonstick spray. Arrange the matzo crackers in a single layer on the foil, breaking them as necessary to fit. (Depending on their size, you may not need to use all of the crackers.)
Melt the butter in a medium saucepan over medium-high heat. Stir in the sugar and kosher salt and bring to a full boil; the mixture should be bubbling all over, not just on the edges. Continue to boil for 2 to 3 minutes, stirring occasionally so the sugar and butter caramelize evenly. Remove from the heat and stir in the vanilla.
Pour the mixture over the top of the matzo. Using a rubber spatula, quickly spread the toffee mixture to coat the matzo. (It does not have to be perfect; the oven will even it out). Bake until the toffee is bubbling, 5 to 6 minutes.
Sprinkle the chocolate chips over the hot toffee in an even layer. Let sit until the chocolate is melted, about 5 minutes. Use an offset spatula to gently spread out the chocolate, then sprinkle with the sea salt, if using. Let sit at room temperature for 1 hour, then refrigerate for another hour to set completely.
Break into pieces and serve, or store in an airtight container at cool room temperature for up to 2 weeks.
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