Start by blooming the gelatin in a small bowl with cold water, letting it sit for about 5-10 minutes until it softens.

In a medium saucepan, combine granulated sugar and water over medium heat. Stir continuously until the sugar dissolves, then allow it to boil without stirring until it reaches the firm ball stage (around 240°F or 115°C).

Once your syrup is ready, carefully remove it from heat and slowly pour the hot syrup into the bowl with the bloomed gelatin. Begin mixing on medium speed and beat until the mixture becomes fluffy and glossy, about 8-10 minutes.

As the mixture starts to thicken, add in the peppermint extract. Continue beating for another 2-3 minutes, ensuring the extract is fully incorporated.

Melt your milk chocolate in a heatproof bowl over simmering water or in the microwave. Once fully melted, gently drizzle it into the fluffy marshmallow mixture.

Prepare an 8x8-inch pan by lining it with parchment paper and dusting the bottom with cornstarch. Pour the marshmallow mixture into the pan, spreading it evenly.

Once set, gently lift the marshmallow slab from the pan and place it on a cutting board. Use a sharp knife coated in cornstarch to cut it into squares or rectangles.