Description

Craving the tart, comforting flavors of rhubarb muffins but looking for a cozy, hands-off twist? Say hello to Slow Cooker Rhubarb Streusel Dessert Casserole! This delightful recipe reimagines the classic muffin as a spoonable, slow-cooked dessert, featuring a soft, cake-like base infused with tart rhubarb and warm cinnamon, topped with a buttery, crunchy streusel that adds a sweet, textured finish.

Ingredients

For the Rhubarb Base

All-Purpose Flour (1 ½ cups): Forms the cake-like structure.
- Substitution: Gluten-free flour blend or whole wheat flour (texture may vary).
Granulated Sugar (¾ cup): Sweetens the base.
- Substitution: Coconut sugar or maple syrup (reduce to ⅔ cup).
Light Brown Sugar (¾ cup, tightly packed): Adds caramelized depth.
- Substitution: Dark brown sugar or coconut sugar.
Baking Powder (1 tsp): Ensures a light texture.
- Substitution: ¼ tsp baking soda + ½ tsp cream of tartar.
Baking Soda (½ tsp): Helps with rise and tenderness.
- Substitution: Increase baking powder to 1 ½ tsp.
Salt (½ tsp): Balances sweetness.
- Substitution: Sea salt or omit if using salted butter.
Ground Cinnamon (1 tsp): Adds warm, spiced flavor.
- Substitution: Nutmeg or allspice.
Unsalted Butter (½ cup, melted): Provides rich flavor.
- Substitution: Vegan butter or coconut oil.
Large Eggs (2): Bind the ingredients.
- Substitution: Flax eggs (1 tbsp flaxseed + 3 tbsp water per egg) for vegan.
Buttermilk (½ cup, or ½ cup milk + 1 tsp vinegar): Adds moisture and tang.
- Substitution: Plant-based milk with vinegar or plain yogurt.
Vanilla Extract (1 tsp): Enhances flavor.
- Substitution: Almond extract or vanilla bean paste.
Fresh Rhubarb (1 ½ cups, diced into ½-inch pieces): Provides tart, juicy texture.
- Substitution: Frozen rhubarb (thawed, drained) or strawberries (for a sweeter twist).

For the Streusel Topping

All-Purpose Flour (½ cup): Forms the crumbly base.
- Substitution: Gluten-free flour blend or oat flour.
Light Brown Sugar (¼ cup, tightly packed): Sweetens the streusel.
- Substitution: Dark brown sugar or coconut sugar.
Ground Cinnamon (½ tsp): Adds spiced warmth.
- Substitution: Nutmeg or cardamom.
Unsalted Butter (¼ cup, cold, cubed): Creates a crunchy texture.
- Substitution: Vegan butter or coconut oil (chill before cubing).

Why They’re Important: The rhubarb delivers a tart, juicy filling, while cinnamon and sugars add cozy sweetness. The buttermilk and eggs create a soft, cake-like base, and the streusel provides a buttery, crunchy finish, making each spoonful a perfect balance of textures and flavors.

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Instructions

Step 1: Prepare the Rhubarb Base

In a large bowl, whisk together 1 ½ cups all-purpose flour, ¾ cup granulated sugar, ¾ cup tightly packed light brown sugar, 1 tsp baking powder, ½ tsp baking soda, ½ tsp salt, and 1 tsp ground cinnamon until well combined.
In a separate bowl, mix ½ cup melted unsalted butter, 2 large eggs, ½ cup buttermilk (or ½ cup milk + 1 tsp vinegar), and 1 tsp vanilla extract until smooth.
Add the wet ingredients to the dry ingredients, stirring gently with a spatula until just combined. The batter will be thick and slightly lumpy.
Gently fold in 1 ½ cups diced fresh rhubarb, being careful not to overmix to preserve the rhubarb’s texture.
- Tip: Dice rhubarb into uniform ½-inch pieces for even cooking. Stir batter minimally to keep it tender. Use a spatula to fold rhubarb gently to avoid crushing.

Step 2: Prepare the Streusel Topping

In a small bowl, combine ½ cup all-purpose flour, ¼ cup tightly packed light brown sugar, and ½ tsp ground cinnamon.
Add ¼ cup cold, cubed unsalted butter and cut in with a fork, pastry cutter, or your fingers until coarse crumbs form (pea-sized pieces).
Set aside or refrigerate until ready to use to keep the butter cold.
- Tip: Keep butter cold for a crumbly texture. Work quickly to avoid melting the butter. Store in the fridge if preparing ahead to maintain structure.

Step 3: Layer in the Slow Cooker

Lightly grease a 4-6 quart slow cooker insert with cooking spray or a thin layer of butter to prevent sticking.
Pour the rhubarb batter into the slow cooker, spreading it evenly with a spatula to create a smooth layer.
Sprinkle the streusel topping evenly over the batter, covering the surface completely. Do not press down; keep the topping loose for a crunchy texture.
- Tip: Use a slow cooker liner for easy cleanup. Spread batter gently to avoid compacting. Distribute streusel evenly for consistent crunch.

Step 4: Slow Cook

Cover and cook on high for 2-3 hours or low for 4-6 hours, until the base is set and a toothpick inserted in the center comes out clean or with a few moist crumbs (not wet batter).
Check doneness at the minimum time; if the streusel looks too wet, remove the lid for the last 30 minutes on high to evaporate excess moisture and enhance crispness.
- Tip: Place a paper towel under the lid to catch condensation and keep the streusel from getting soggy. Avoid lifting the lid too often to maintain heat. Cooking times vary by slow cooker model.

Step 5: Serve

Turn off the slow cooker and let the dessert cool for 10 minutes to set slightly, making it easier to scoop.
Scoop the warm rhubarb casserole into 8-10 bowls or dessert cups (about ½ cup per serving), ensuring each portion has a mix of tender rhubarb base and crunchy streusel.
Serve warm with a scoop of vanilla ice cream, whipped cream, or a drizzle of custard for a complete dessert experience. Pair with coffee, herbal tea, or a dessert wine (like Sauternes) for a cozy touch.
- Tip: Use a large spoon for a rustic presentation. Serve immediately for the best texture contrast. Offer extra streusel crumbs or a sprinkle of cinnamon on the side for customization