Instructions

Using stand mixer fitted with whisk attachment, whip cream on medium-low speed until foamy, about 1 minute. Increase speed to high and whip until soft peaks form, 1 to 3 minutes. Cover bowl with plastic wrap and refrigerate until needed.
Working in 2 batches, grind Sucanat in spice grinder until fine and powdery, about 1 minute. Combine 6 tablespoons ground Sucanat and ¼ cup water in small saucepan and bring to boil over medium-high heat. Cook until slightly thickened and syrupy (mixture should register about 235 degrees), about 4 minutes. Remove syrup from heat and cover to keep warm.
Microwave chocolate, cocoa, and remaining 3 tablespoons water in bowl at 50 percent power, stirring occasionally, until melted and smooth, about 1 minute.
Using clean, dry mixer bowl and whisk attachment, whip egg whites and cream of tartar on medium-low speed until foamy, about 1 minute. Increase speed to medium-high and whip whites to soft, billowy mounds, about 1 minute. Gradually add remaining 2 tablespoons ground Sucanat and whip until glossy, stiff peaks form, 2 to 3 minutes.
Reduce speed to medium and slowly add warm syrup, avoiding whisk and sides of bowl. Increase speed to medium-high and continue to whip until the meringue has cooled slightly and is very thick and shiny, 2 to 5 minutes. Add warm melted chocolate and vanilla and continue to whip until incorporated, about 1 minute.
Gently fold one-third reserved whipped cream into meringue with rubber spatula. Fold in remaining whipped cream and ½ cup hazelnuts until just incorporated.
Divide mixture evenly between eight 6-ounce ramekins and gently tap ramekins on counter to settle batter. Wrap ramekins tightly with plastic wrap, making sure wrap doesn’t touch semifreddo, and freeze until firm, at least 4 hours or up to 5 days. Before serving, let semifreddo soften at room temperature for 5 to 10 minutes, then sprinkle with remaining chopped hazelnuts.