Preheat oven to 350 degrees (F). Grease a 9×9-inch pan, line with parchment paper, then grease the parchment paper.
In a medium saucepan over medium heat, melt butter and sugar together - whisking occasionally - until the butter is just melted. Remove from the burner. Add the peanut butter and milk, mix together well, and allow the mixture to cool for 2-3 minutes. Quickly whisk in the egg and vanilla extract.
Whisk together salt and flour. Add dry ingredients all at once to the wet ingredients. Stir until just incorporated.
Pour the batter into the prepared pan and smooth the top with a rubber spatula. Sprinkle the top with the granulated sugar. Bake for 14- 18 minutes, or until the edges are golden and the center is set.
Right after removing the pan from the oven, carefully press the kisses into the top of the hot blondies. Let cool completely before cutting.
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