Blondie Sundaes with Fried Walnuts and Candied Fennel

Add sugar and whisk until smooth.

Whisking constantly, add egg yolks one at a time followed by whole egg, beating after each addition to fully incorporate before adding more.

Add dry ingredients and mix until smooth.

Scrape batter into prepared dish; smooth top.

Bake blondies until lightly browned and center is firm when gently pressed, 15–20 minutes.

Transfer dish to a wire rack and let cool.

Cut into 16 bars.

Preheat oven to 350°F.

Toast walnuts on a rimmed baking sheet, tossing once, until golden brown, 5–8 minutes.

Let cool slightly; place in a heatproof jar or airtight container.

Heat sugar and 1 cup water in a medium saucepan over medium, stirring, until sugar dissolves.

Let cool slightly; then pour over walnuts.

Seal jar and let sit at least 12 hours and up to 1 day.

Pour walnuts into a fine-mesh sieve set over a clean medium saucepan and let syrup drain into saucepan, tossing walnuts to shake off excess.

Transfer walnuts to a medium bowl.

Reserve sieve.

Add sliced fennel and lemon zest to syrup; scrape in vanilla seeds and add pod.

Bring to a simmer over low heat.

Cook, stirring occasionally, until fennel is translucent and tender, 20–25 minutes.

Discard pod; let fennel cool in syrup.

Fit another medium saucepan with thermometer; pour in oil to come 2" up sides of pan.

Heat oil over medium-high until thermometer registers 350°F.

Add powdered sugar to walnuts and toss to coat.

Place in reserved sieve and shake off excess sugar.

Carefully add walnuts to oil and cook, turning with a spider or slotted spoon to prevent sticking, until brown and crisp, about 3 minutes.

Transfer to a parchment-lined rimmed baking sheet; let cool.

Break up any clumps.

Scoop gelato into bowls.

Top with ground cherries, blondies broken into large pieces, walnuts, candied fennel, and fennel fronds.

Blondies can be made 2 days ahead.

Store tightly covered at room temperature.

Walnuts can be fried 2 days ahead.

Let cool; store airtight at room temperature.

Fennel can be candied 2 days ahead.

Let cool in syrup; transfer to an airtight container and chill.