In a saucepan, bring the maple syrup, sugar, corn syrup and water to a boil. Simmer until a candy thermometer reads 105 °C, about 30 minutes. Let the syrup cool.
Cut the phyllo sheets in half to make rectangles of the same size as the baking dish.
Place 5 sheets at the bottom of the pan, brushing with butter between each sheet. Sprinkle with about 250 ml (1 cup) of pecans. Cover with 3 more phyllo sheets brushed with butter. Sprinkle again with pecans. Continue to alternate layers of dough and pecans with the remaining ingredients.
Do not fill the pan more than three-quarters of its capacity.
Bake in the middle of the oven for about 35 minutes or until lightly browned. Right out of the oven, pour all the syrup over the baklava (for the sweet tooth), or about three quarters of the syrup if you want a slightly less sweet baklava. Let stand overnight before cutting into pieces.