Combine butter, and 2 and 1/3 cups chocolate morsels in a heavy saucepan.
Cook over medium heat, stirring occasionally, until butter and chocolate melt together.
Set aside to cool while preparing other ingredients.
In a small mixing bowl, combine flour, baking powder, and salt and stir to combine.
In a large mixing bowl, beat eggs, sugar, and vanilla at medium speed until combined and fluffy, about 60 seconds.
Add flour mixture gradually to bowl, beating well. Reduce speed if needed to avoid a mess.
Pour in chocolate mixture and beat well.
Stir in remaining 1 and 1/2 cups chocolate chips/chunks.
Line a baking sheet with parchment paper, or non-stick mat. (You may also use a non-stick baking spray or pan).
Make balls the size of about 1 tablespoon and place on baking sheet.
Bake at 350° for 7-8 minutes, or until tops are glossy. Cool for about 2 minutes on sheet or until set.
Remove to wire rack to cool completely.