Step 1

Preheat an air fryer to 350°F (180°C).

Step 2

Make the espresso simple syrup: In a small saucepan, combine the water, sugar, and espresso powder and bring to a boil over medium-high heat. Let the mixture simmer for 5 minutes, then remove the pot from the heat and set aside until ready to use. The syrup will keep in an airtight container in the refrigerator for up to 1 week.

Step 3

Make the coffee-yogurt custard: In a small bowl, whisk together the yogurt, espresso powder, and egg.

Step 4

Assemble the toast: Set the grapefruit on a cutting board and use a sharp knife to cut off the top and bottom so the flesh is exposed and the fruit can sit upright. Use the knife to remove the rind from around the fruit, following the contours of the fruit and cutting carefully to remove all of the pith, but leaving as much flesh intact as possible. Holding the fruit in your non-dominant hand, use the knife to cut between the membranes to release the segments.

Step 5

Place the croissant halves, cut-side up, on a flat surface and use your fingertips to gently press down the centers to create wells. Brush each croissant half with the espresso syrup, then spoon a couple of tablespoons of custard into each well and lightly spread to fill evenly. Arrange the grapefruit segments on top of the custard and sprinkle with the sugar.

Step 6

Carefully transfer the filled croissants to the air fryer and cook until the edges of the pastry are golden brown and the custard has set in the center, 5–7 minutes. Remove from the air fryer and transfer to a plate. If you want a little more color and crunch, use a kitchen torch to caramelize the sugar on the grapefruit.

Step 7

Serve immediately.

Step 8

Enjoy!