Preheat oven to 350°. Line an 8-inch square metal pan with nonstick foil or line with regular foil and grease foil with some extra butter (or cooking spray).
Set the sheet of matzo in the pan.
Put the butter in a microwave-safe 2 cup measure (I use a Pyrex liquid measuring cup) and heat the butter for 30 seconds or until it is partially melted. Add the brown sugar and stir until smooth.
Put mixture in microwave and microwave for 2 minutes, stirring every 30 seconds (important!). Pour over the matzo.
Bake at 350 for 10 minutes or until caramel is very hot and bubbly. Remove from oven and let cool on a wire rack very briefly -- just about 3 minutes or until caramel settles down.
Sprinkle chocolate chips evenly over hot caramel. Set a flat pan on top of the square pan to help hold in the heat. Let stand 5 minutes to soften chips, then spread softened chocolate chips over caramel. Sprinkle nuts over the top.
Refrigerate until chocolate and caramel have hardened, about 1 hour. Break or cut bark.
Note: To toast nuts, bake in a shallow pan in a 350° oven for 5-10 minutes or cook in a skillet over low heat until lightly browned, stirring occasionally.