In large bowl, cream softened butter using electric mixer or rubber spatula.
Add brown sugar and beat on medium speed until combined.
Add vanilla extract and egg yolk and mix to combine.
Add in flour and salt and mix until just blended.
Press dough in ungreased pan, 13x9x2 inches. Use a rubber spatula or your fingers to completely spread to edges of pan.
Bake 25-30 minutes or until very light brown (crust will be soft).
Remove pan from oven and immediately sprinkle milk chocolate chips on warm baked crust. Let stand about 5 minutes or until chips are softened (they will look a little shiny, that's when you know they are softened). Using a knife or small spatula, spread melted chocolate chips evenly on crust until fully covered.
Sprinkle with sliced almonds.
Cool 30 minutes in pan on a wire rack. Then, while still slightly warm, cut into bars, 4 rows by 6 rows.