In large mixer bowl beat butter, then add in sugar and mix.
Add in peanut butter and mix well.
Add in vanilla and flour and mix until completely combined the dough is a dry shortbread dough,
when you press it together in your hands it should stick together.
Press dough together into a ball in the bowl, then turn out onto your counter.
Cut dough in half and roll each portion between wax paper sheets to 1/4" thick and cut the cookie dough with a 2-1/2 inch circle cookie cutter.
I use wood dowels that are 1/4" so the dough is all even.
Fold the dough to create a creased edge, then do the other two corners to create a triangle.
Fill with jelly/preserves I find it easy to put it in a plastic bag and pipe it into the triangles.
Bake at 350 degrees for 10-12 minutes.
Allow cookies to cool completely.