Easy Apple Crumb Bars

Ingredients

For the shortbread crust:

• Unsalted butter.
• All-purpose flour.
• White, granulated sugar.

For the apple filling:

• Apples: I use granny smith apples exclusively (the green ones, my absolute favorites for baking due to their tartness). They bring some acid to the mix that complements the overall sweetness of the cake. And they hold their shape and don't turn mushy in the oven. If you have another favorite that you usually bake with (pink lady, fuji, gala, Honeycrisp apples), by all means, use it.
• Brown sugar: light or dark.
• Cinnamon: any ground cinnamon you normally use works fine. I like Frontier Vietnamese cinnamon and Simply Organic Ceylon cinnamon. Or use a store-bought or homemade apple spice mix.

For the crumb topping:

• Unsalted butter.
• White, granulated sugar.
• Brown sugar: light or dark.
• All-purpose flour.

See the recipe card at the end of this post for quantities.

Kitchen notes

• Organization: read the recipe first and ensure you have ingredients at the correct temperature, equipment, and enough workspace. This will make the process so much easier.
• Baking time: keep in mind that all ovens and pans are different, even if they look the same or very similar. The baking time in my recipes is as accurate as it can be, but it might take you more or less time. You can use a thermometer(like the OXO oven thermometer) to check that your oven is at the right temperature. I recommend you keep track of how your oven works and what tiny details you need to adjust. 
• Apples: peel and cut at the last minute to avoid them turning brown as much as you can. Use a mandoline for thin slices (like the ones in this post) or a kitchen knife to cut thicker ones. 
• Make-ahead: the base and the crumble can be made ahead and frozen for a month or kept in the fridge for a week. 
• Flavorings: use other spices and/or citrus zest to change the flavor slightly.

The shortbread base

I have my favorite recipe for this type of base that I use for different bars and squares, like the raspberry apple bars or the honey walnut bars if using powdered sugar.

It never fails as long as you remember the measuring unit is volume, like cups:

• 1 measure of flour
• ½ measure of butter
• ¼ measure of sugar

You can add a pinch of salt, spices, citrus zest, and other flavorings. But the main recipe is perfect and goes well with any topping, give or take.

The result is crumbly, and you can easily pat it on the bottom of the pan.

For this recipe, I prick it with a fork and freeze it before pre-baking it. This step will make it crunchier and less soggy once the apple filling is added.

Mix ingredients in a large bowl and then put in the baking pan. Distribute it throughout the bottom.

Press it with your hands until it's all compacted and there are no crumbly parts.

Prick it with a fork and freeze it before pre-baking it.

Bake it for 15 minutes, until it's starting to dry and puff. This will help to avoid it being soggy when you add the filling.

Vintage Kitchen tip: chilling or freezing the shortbread crust before lightly baking it (called blind baking) prevents it from shrinking and puffing up too much.

The apples

• Granny smith: these are my favorites by far because they are acid enough to balance out the butter and sugar used in the recipe. But of course, you can use your favorite baking apples. I know many seasonal ones are delicious. 
• Cutting them: you can slice them thicker or thinner. Take into account that very thin slices (cut with a mandoline for example), will bake softer than thicker ones which will remain crunchier. It comes down to personal taste; some people like very soft apples in their desserts, while others, like my father, will only eat this dessert if the apples are still firm. 

Crumble topping

Another basic and super easy component of these apple bars, it's a simple mix of flour, sugar, and butter known as streusel or crumb topping.

You can integrate it by hand, with a fork or pastry cutter.

• Make-ahead: crumble can be made in advance and frozen for a few months. Or in the refrigerator, where it lasts at least a few weeks. Add it directly to crumbles, muffins, coffee cakes, or bars.