Wash the strawberries under cool running water and pat them completely dry with paper towels, making sure to remove all moisture from the stems and surface. Moisture is the enemy of chocolate coating—it causes the chocolate to seize and won't adhere properly. Set the dried strawberries aside on a clean plate or parchment paper while you prepare the chocolate.
Place the white chocolate chips and 1 teaspoon of coconut oil in a heat-safe bowl. If using a double boiler method, set the bowl over simmering (not boiling) water, stirring occasionally until melted and smooth—this gives you more control than microwaving. If using the microwave, heat in 30-second intervals, stirring between each, until fully melted. The coconut oil helps thin the chocolate to the perfect dipping consistency without affecting the flavor. I always use a double boiler for white chocolate because it's more forgiving and less likely to seize.
Holding a strawberry by the stem, dip it into the melted white chocolate, tilting and rotating to coat the entire berry while leaving the stem exposed. Lift it out and gently tap off excess chocolate back into the bowl, then immediately place it on a parchment-lined baking sheet. Work quickly but carefully—if the chocolate begins to set, gently rewarm it. Once all strawberries are dipped in white chocolate, immediately sprinkle the nonpareils over the coating while it's still wet so they adhere properly.
Place the baking sheet with white chocolate-coated strawberries into the refrigerator for 15-20 minutes until the chocolate is completely set and hard to the touch. This gives you a firm base so the dark chocolate coating won't mix with the white layer.
While the white chocolate sets, melt the dark chocolate chips with 1 teaspoon of coconut oil using the same method as Step 2. Dark chocolate can handle slightly higher temperatures than white chocolate, but still avoid overheating. The coconut oil again helps achieve a smooth, pourable consistency ideal for dipping.
Remove the chilled white chocolate-coated strawberries from the refrigerator. Using the same dipping technique as Step 3, hold each strawberry by the stem and dip it into the melted dark chocolate, rotating to coat the lower half or two-thirds of the berry, creating a contrast with the white chocolate layer underneath. Return each dipped berry to the parchment-lined baking sheet and immediately add sprinkles to the dark chocolate while wet. Once all strawberries are dipped and decorated, refrigerate the finished strawberries for at least 20-30 minutes until fully set. I like to keep them in the fridge until ready to serve—they stay fresh and firm for up to 3 days.