Set oven to 350F and line muffin cups with paper liners.
In a large bowl, combine flour, sugar, baking powder, and salt. Cut in the peanut butter and cold butter, using a pastry cutter, until entire mixture becomes well incorporated.
In a small bowl, beat together the eggs and milk. Stir egg/milk mixture into the flour mixture just until evenly moistened. Fill lined muffin cups halfway. Drop in about a tablespoon of fruit preserves/jelly over each muffin cup. Fill rest of muffin cups to the top with the rest of the batter, smoothing the tops evenly.
Bake for about 23 minutes or until a toothpick inserted in the middle comes out with just a few tender crumbs attached. Cool muffins completely. Sprinkle with powdered sugar upon serving, if desired.