In a small saucepan over low heat, melt butter and dissolve sugar slowly, stirring. Once sugar is dissolved, let simmer until the caramel begins to bubble and becomes a slightly darker brown. Be careful not to let it burn!
Preheat oven to 400 F. Lay broken up matzah pieces flat on a cookie sheet, side by side, trying to fill in any gaps. Pour the caramel mixture over the top evenly. Spread with spatula if needed, trying to cover as many of the matzahs as you can.
Sprinkle chocolate over the top.
Bake in oven for 5 to 8 minutes, or until caramel bubbles. Remove from oven and spread chocolate with a spatula to form a coating.
Sprinkle with flaky salt.
Refrigerate for about an hour (or freeze about 20 minutes) until hardened.