In a medium saucepan, combine sugar, lemon slices, and water; bring to a boil. Reduce heat and simmer until sugar dissolves and the mixture is syrupy about 10 minutes. Set aside to cool.
Meanwhile, heat all ingredients for the raspberry filling over medium-low heat until chocolate is melted. Remove from the heat.
In a medium-size bowl, beat together the eggs and sugar using an electric mixer. Add sour cream, oil, and semolina. Mix just to combine. Set aside.
Unroll the fillo dough. Trim the whole stack, if necessary, to fit the 11-inch round or 9x13-inch baking pan (the easiest way to do this is to put the pan over fillo sheets and cut the excess with a sharp knife). Separate the sheets in half. Cover with a clean cloth to keep from drying out as you work. If you work fast enough, you don’t need to cover it.
Preheat oven to 350 degrees Fahrenheit.
Using the half stack of fillo, place two sheets of fillo dough in a greased baking pan. Spread with 3-4 tablespoons of the semolina mixture. Repeat with the remaining sheets, topping with the mixture after each sheet.
Add the raspberry filling and distribute evenly.
Continue layering the other half of fillo dough and semolina mixture, finishing with two layers of fillo on the top.
Using a sharp knife cut the unbaked baklava into squares or diamonds all the way to the bottom of the pan. Lightly sprinkle the top of pastry with cold water. This inhibits the pastry from curling.
Bake baklava for 50-60 minutes or until golden and crisp. Remove from the oven and immediately spoon syrup over it (always pour cold syrup over hot baklava or vice versa).
Let cool for at least 4 hours or overnight before serving. Keep refrigerated.
Substitute raspberries with cherries or your favorite berries (or a mix of berries).