Begin by preheating your oven to 350 degrees F.
Then in a bowl, mix together the flour, baking soda, and salt. Set this aside.
With a mixer on medium speed, cream together the butter, peanut butter, sugar, and brown sugar until light and fluffy. This should take about 4-5 minutes. Then add the egg and vanilla. Mix to combine. Reduce the mixer speed to low and add the dry ingredients. Mix until just combined.
Shape the dough into 1-inch balls and place in cups of a miniature muffin pan.
Bake for 8 to 10 minutes, or until the cookies are lightly brown and still puffy. Remove from the oven and press a peanut butter cup in the middle of each cookie. Once the chocolate starts to melt on the top, add a pinch of sprinkles. Cool for about 10 minutes before removing from the pans; then allow the chocolate to firm up completely.