Rosemary dots these sugared pear desserts.
Melt the butter and sugar in a large saute pan over medium-high heat. Cook, stirring frequently until sugar begins to caramelize, about 2 minutes. Add the pears and rosemary, raise heat to high, and cook, stirring occasionally, until pears are browned and caramelized all over, 3 to 5 minutes. (If pears begin to burn, reduce heat to medium.) Remove the pears, and spread out on a plate to cool.
Place saute pan back on high heat, and add 1/4 cup water, stirring up the browned sugar and butter. Cook, stirring and swirling pan, until reduced to a thick syrup.
Layer pears in four small glasses, alternating with the sour cream for two layers of each. Drizzle some of the syrup over each serving, sprinkle with crystal sugar, and serve.
Buy pears that are ripe but still firm so they don't get too soft while cooking.