Strawberry Rhubarb Miniature Tarts

1 ½ cups crushed pretzels

¾ cup butter, melted

½ cup crushed walnuts

¼ cup brown sugar, packed

2 tablespoons maple syrup

1 pinch ground cinnamon

1 pinch ground cardamom

2 egg whites

1 cup raw sugar

2 tablespoons self-rising flour

1 teaspoon vanilla extract

¾ pound rhubarb, finely diced

2 cups finely chopped fresh strawberries

Preheat oven to 350 degrees F (175 degrees C). Grease 12 muffin cups.

Stir pretzel crumbs, butter, walnuts, brown sugar, maple syrup, cinnamon, and cardamom in a bowl until mixture is well combined and loose. Spoon pretzel mixture into the bottom of prepared muffin cups, filling them about 1/4 full. Press the crust down.

Beat egg whites in a large mixing bowl until frothy, and mix in raw sugar, self-rising flour, and vanilla extract to make a batter; stir in rhubarb and strawberries. Spoon fruit mixture over pretzel crust, filling muffin cups to the top.

Bake in the preheated oven until the fruit filling is bubbling and golden brown on top, about 30 minutes. Cool 10 to 15 minutes; serve warm.