M&M Shortbread Cookie Bars with Chocolate
A three-layer bar cookie combining buttery shortbread with melted milk chocolate and colorful M&M's. The shortbread base bakes briefly before the chocolate layer is added, then topped with another layer of dough and candies for a texture that's crisp on the edges, chewy in the middle, and studded with chocolate chips and candy shells. This is a crowd-pleasing dessert that works for potlucks, bake sales, or casual family gatherings. What sets this version apart is the strategic two-stage baking method: the base crust prebakes to prevent sogginess, while the top layer stays slightly softer, creating contrast. The sweetened condensed milk ensures the chocolate layer sets smoothly without graininess, and the M&M's add visual appeal and pops of color that make these bars feel festive without requiring decorating skills.
Ingredients
- 1 cup butter, softened
- 1 egg
- ¾ cup sugar
- 1 tsp vanilla
- 3 cup flour
- ½ tsp baking powder
- 14 oz sweetened condensed milkevaporated milk + 1/4 cup sugar14 oz evaporated + 1/4 cup sugartexture change
slightly thinner consistency, less sweetness
Full guide → - 1 ½ cups milk chocolate chips
- 1 cup M&M'schopped nuts (pecans, walnuts)3/4 cuptexture changeadds tree_nuts
adds crunch, removes color appeal
- water(optional)
Instructions
- 1
Preheat oven to 350 degrees.
- 2
Mix together softened butter, egg, sugar, and vanilla until combined.
- 3
Stir in flour and baking powder.
- 4
Add water one tablespoon at a time if needed until dough holds together.
- 5
Press two-thirds of the dough into a lightly greased 9x13 cake pan.
- 6
Bake for 5 minutes.
- 7
While the crust bakes, combine sweetened condensed milk and milk chocolate chips over low heat, stirring until melted and smooth.
- 8
Pour chocolate mixture over the partially baked crust.
- 9
Crumble or sprinkle remaining dough over the chocolate layer.
- 10
Scatter M&M's over the top.
- 11
Bake for 15-20 minutes until the top layer is lightly browned.
- 12
Cool on the counter for at least 15 minutes, then refrigerate for 1 hour to set before cutting.
Tips
Prebaking the shortbread base for 5 minutes is critical: it sets the structure and prevents the bars from becoming soggy when the chocolate layer is added. Skipping this step results in a mushy bottom layer.
Cool the bars completely in the refrigerator for the full hour before cutting. This allows the sweetened condensed milk and chocolate to set firmly, so bars cut cleanly without crumbling or smudging.
Press the dough firmly but gently into the pan with the heel of your hand or the bottom of a measuring cup for an even, compact base layer that won't have gaps.
Good to Know
Airtight container at room temperature for up to 4 days, or refrigerated for up to 1 week.
Bars can be made up to 2 days ahead. Store covered in the refrigerator. Do not freeze; the texture of the condensed milk layer becomes grainy when thawed.
Serve at room temperature or slightly chilled. Pairs well with milk, coffee, or tea.
Common Mistakes
Skip the 5-minute pre-bake of the base to avoid a soggy bottom layer when the chocolate mixture is added.
Don't skip the 1-hour refrigeration to avoid bars that fall apart or smudge when cut.
Substitutions
Dairy-Free Swaps
General Alternatives
adds crunch, removes color appeal
slightly thinner consistency, less sweetness
Full guide →FAQ
Can I freeze M&M Shortbread Cookie Bars?
Freezing is not recommended. The sweetened condensed milk filling becomes grainy and separates when thawed, affecting texture and consistency. Store refrigerated instead for up to one week, or at room temperature for up to four days.
What if I don't have milk chocolate chips?
Dark chocolate chips, semi-sweet chips, or even white chocolate chips work well. Dark chocolate will result in a less sweet, more sophisticated flavor. White chocolate creates a milder taste. Use the same 1 1/2 cup quantity and melt over low heat as directed.
How long do these bars keep after cooling?
At room temperature in an airtight container, bars stay fresh for up to 4 days. Refrigerated, they last 1 week and may have a firmer texture. Do not freeze due to the condensed milk layer becoming grainy upon thawing.