Preheat oven to 350°F (175°C).

In a medium-sized bowl, sift together the flour and baking powder; set aside.

Place the butter and the semi-sweet chocolate chips in a small saucepan and heat over medium heat until melted and smooth. Set aside to cool slightly.

Crack the eggs in a large mixing bowl, then add in the sugar and vanilla extract.

With an electric mixer on medium speed, beat the egg mixture for 10 minutes, or until pale and creamy.

Gently stir the sifted flour mixture into the beaten egg mixture until just combined.

Fold in the melted chocolate mixture followed by the butterscotch chips. Let the dough stand for 10 minutes.

Line two baking sheets with parchment paper.

Drop dough by rounded tablespoonfuls onto the prepared baking sheets, about 2 inches apart.

Bake for 9 to 11 minutes, or until the edges are set and the tops are dry and slightly cracked.

Cool the cookies on the baking trays for a few minutes before transferring them to a wire rack to cool completely.