In this Instructable, I'll show you how to use a spherification technique to create a classic dessert with a science-y twist.

This strawberry shortcake includes a sponge cake base, white chocolate chantilly, and popping strawberry spheres. It is sure to impress your guests!

This recipe involves sodium alginate and calcium chloride, two food-safe compounds that help form the popping spheres. Mine came with a molecular gastronomy kit, but they can also be purchased online or in specialty food stores.

Step 1: Gather Ingredients

(Makes 3 servings)

For alginate bath:

2 cups of water

5g of sodium alginate

For strawberry puree:

1 1/2 cups of strawberries

1 tsp vanilla

2 tbsp of sugar plus more to taste

1/2 tsp calcium chloride

For microwave sponge cake:

1/4 cup + 2 tbsp all-purpose flour

2 tbsp granulated sugar

1/4 tsp baking powder

1/8 tsp salt

1/4 cup + 2 tbsp milk

1/2 tbsp vanilla extract

2 tbsp butter, melted

For white chocolate whipped cream:

1/4 cup heavy whipping cream

1 tbsp melted white chocolate

1 tbsp powdered sugar, plus more to taste

Step 2: A Bit of a Scientific Explanation

The spherification technique used here can be used in a wide variety of savory and sweet applications, not just strawberry puree. This recipe is intended to be an introduction to the technique so it can also be used in later recipes.

How does it work?

Sodium alginate is a gelling agent derived in various types of algae. When it comes in contact with certain ions, such as calcium, it forms a cross-linked gel polymer. Because the strawberry puree contains calcium chloride, when the mixture is submerged in the alginate solution, the alginate reacts with the surface of the puree and forms a thin membrane. This gel membrane surrounds the still-liquid puree, which causes the popping sensation when the membrane is broken.

Step 3: Puree Strawberries

Using a blender or hand blender, puree the strawberries, sugar, vanilla, and calcium chloride until completely smooth.

Step 4: Mold and Freeze Strawberries

Pour the puree into an ice cube tray, preferably one with round sections. These don't have to be exactly spherical, though, because once melted, the final spheres will take on a more rounded shape. Cover with plastic wrap and freeze.

While some recipes do not use this extra molding and freezing step, I find that it makes the spherification process much easier. The cube tray ensures that the spheres are each a uniform shape, and the puree is easier to work with as a solid.

Step 5: Prepare Alginate Bath

Using a blender, food processor, or hand blender, mix the alginate and water until completely dispersed. The liquid will look cloudy and bubbly at first, so place in fridge to chill for at least 20 minutes to let it settle.

Step 6: Make Sponge Cake Base

For small disks, I find a microwave mug cake to be the fastest and easiest way to make the base. This is my favorite recipe, adapted from tablefortwoblog.com

In a mug, whisk together the dry ingredients, then add milk, vanilla, and butter until there are no more lumps.

Microwave on high for two minutes.

One cooled, remove from the mug and carefully divide into three disks. These will be covered with whipped cream later, so don't worry if they look uneven.

Step 7: Make White Chocolate Chantilly

In a cold bowl, whisk together the cream, vanilla, and sugar until the mixture begins to thicken and resemble whipped cream. Then, carefully stir in white chocolate.

Step 8: Spherify Strawberries

Prepare the alginate bath and a bowl of water for rinsing.

Unmold frozen strawberry cubes and let thaw slightly. Using a spoon, lower each cube into the sodium alginate solution. Make sure they are not able to touch each other to prevent clumping. After about ten seconds, carefully remove each one from the solution and rinse in the water.

The longer they are in the alginate solution, the more durable the spheres will be, but they will have a thicker membrane, which makes them less juicy/poppable. Err on the side of less time in the solution.