In a large mixing bowl, beat together 1/2 cup butter and granulated sugar with electric mixer until well combined and creamy. Beat in egg and vanilla until well combined.
In a separate small bowl mix together flour, baking powder, and salt until well combined. Beat into butter/sugar mixture until well combined. Wrap dough up in plastic wrap and refrigerate for 2-3 hours or until well chilled (can refrigerate overnight or up to a few days).
Preheat oven to 350 degrees F. Lightly spray baking sheets with nonstick spray or line with parchment paper or silpats.
Roll the cookie dough into 24 balls. Place on baking sheets. Bake at 350 degrees F for 14-17 minutes. Cool slightly then move to wire racks to cool completely.
In a large mixing bowl beat together 1/4 cup butter, powdered sugar, and pudding with electric mixer on medium speed until just combined. Slowly beat in milk one tablespoon at a time until spreadable consistency.
Frost cookies then sprinkle nuts on top.
SNAPPY TIPS: The cookie dough can be stored in the refrigerator for a few days until you’re ready to bake. Be sure to add the milk slowly to the frosting so that it doesn’t become too thin. If it does get too thin add a little more butter and powdered sugar.SNAPPY SUBSTITUTIONS: You can try any kind of nut or omit the nuts all together or try something else that is crunchy like chopped cereal. You could also use sprinkles or mini chocolate chips. Any kind instant pudding mix would work well so try any flavor!