Pistachio Pesto Skillet Pasta with Caramelized Brussels Sprouts

• 1 tbspbutter
• 2 tbspolive oil
• ½medium onion
• 3 cupsshredded Brussels sprouts
• 1 tbspsugar
• 1 lbpasta {I used brown rice fusilli — but you can use your favorite}

For Pistachio Pesto

• ½ cupshelled pistachios — unsalted
• 2 cupsfresh basil
• 2small garlic cloves
• 1 tbsplemon juice
• ½ tspsea salt
• 0.4 cupolive oil
• ¼ cupgrated Pecorino cheese — or grated Parmesan cheese