In a non-aluminum pan, bring cream to a boil with the lemon grass and scraped vanilla beans. Simmer on very low heat for 20 minutes. Mix will reduce about 20 per cent. Pull off heat and store overnight. The next day, strain the lemon grass and vanilla beans out and lift to whip cream stage. Bring yolks, eggs, and sugar to ribbon stage, whisking constantly over a bain marie. (110 degrees). Using a mixer, whip at high speed for 10 minutes until the mix is pale in color and light. Fold in the lifted cream. Place in molds and freeze at least 4 hours, preferably overnight.
PINEAPPLE SALSA: In a non-stick pan, heat all together and serve warm with the frozen parfait.