Preheat the oven to 375°F. Line a sheet tray with a layer of foil, then cover the foil with a sheet of parchment. Evenly cover the sheet tray with matzos. Break or cut the matzos into smaller pieces if necessary.
In a heavy bottomed saucepan, combine the butter, brown sugar, and a generous pinch of sea salt. Cook over medium heat, whisking constantly, until the mixture comes to a boil (about 2 to 4 minutes). Boil for 3 additional minutes and continue stirring constantly.
Remove from the heat and pour the toffee mixture over the matzos.
Use a spatula to spread evenly across the entire surface of the matzo. Make sure you spread it out fairly quickly or it will start to get sticky and become harder to smooth over.
Place the baking sheet in the oven and immediately reduce the heat to 350 degrees F. Bake for 15 minutes. Check frequently to be sure that the mixture is not burning. If it appears to browning too quickly, remove the tray from the oven and reduce the heat to 325 degrees F, then replace the tray when the temperature drops a bit.